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In my writing about wealth concentration and oligarchy, I ~~steal a lot from~~ lean heavily on the truly work of Gabriel Zucman, who is a hugely important researcher (winner of the 2023 Clark Medal) who is also starting to play a major role in policy. I’ve talked to him before, but this seemed like a good time to bring him back.

. . .

TRANSCRIPT:
Paul Krugman in Conversation with Gabriel Zucman

(recorded 7/23/26)

Paul Krugman: So, hi everyone. Paul Krugman here, bringing back Gabriel Zucman, probably the best guy for thinking about inequality, especially wealth issues. And since I’ve been writing about that and stealing a lot of Gabriel’s research, I thought we should talk again. So, hi Gabriel.

Gabriel Zucman: Hi Paul, thanks for having me on.

Krugman: Yeah. So, you have been writing—and now I’ve been, you know, cannibalizing it—a lot about wealth concentration. Why don’t you tell us about your reasons for focusing on wealth.

Zucman: Basically, because there’s a fundamental tension in democratic societies between extreme wealth and the very possibility of a well-functioning democracy. And it’s not a new idea—don’t get me wrong. All the thinkers of democracy have written about this, all the way back to Aristotle, more than two thousand years ago.

Krugman: Right.

Zucman: But there was a period of time after World War II when many people thought that this issue belonged to the past. And it corresponded to a very particular moment in history when extreme wealth had largely disappeared after World War II, after the shocks of the first half of the twentieth century.

But now, of course, it’s making a dramatic comeback. And so we are back to this discussion of: how do we deal with this tension? How do we organize the economy and our society to prevent the forms of capture of the political process, in particular, that are associated with extreme wealth?

Krugman: Now, there’s a question. I mean, I’ve been on the inequality beat for an alarmingly long time—since you were a small child, actually. But in the early nineties, let’s say, it was all income rather than wealth. And a lot of it was top quintile, and maybe top one percent. And now you’re telling us that we need to focus on the wealth rather than the income of the top 0.0002 percent. Why that shift? Why wealth rather than income?

Zucman: Well, it’s for two reasons. Number one is a macroeconomic reason, which is that wealth as a whole has been growing much faster than income. So if you look at the ratio of total household wealth to GDP in the US in 1980, it was around 200–250%, and today we are past 500%. This means that the total wealth of the country is equivalent to more than five years of annual production, five years of annual GDP. The second reason is that wealth itself has become much more concentrated, and the rise of wealth inequality, especially at the top of the distribution—at the very top—has been massive and has been even faster and stronger than the rise of income inequality.

So we all know about the rise of the top one percent; the top one percent’s share of total income has increased from about ten percent of income in the US in 1980 to about 20% today. But at the top of the wealth distribution, the increase has been even much more dramatic than that.

Krugman: At the risk of derailing it slightly, one thing that I myself have gone back and forth on—and certainly I get from comments on things I write—is a question comparing the wealth of the top 0.001%, or whatever: should we be comparing it to total wealth or to total income? And I know you’ve used wealth to GDP, and I have some thoughts, but you’ve done it both ways. Which do you use, and why would you use it? I don’t know which is right, but what are your thoughts?

Zucman: I think both statistics are interesting and capture different aspects of reality. So if you’re interested in wealth inequality, in the concentration of wealth, the most meaningful statistic is to divide the wealth of the super-rich by total wealth in the economy. So, for instance, if you look at billionaires—roughly the top 0.1 percent of the population—they own about seven percent of total US wealth today. In 1980, they used to own about one percent of total US wealth. So it gives you a sense of the rise in wealth concentration. If you look at the super-top, you know, the oligarchs, the twenty wealthiest families—a very, very small fraction of the population—their total wealth is 2.0 to 2.2% of total household wealth in the economy. So I think that if you care about wealth inequality, these are the relevant numbers.

Now, it’s also interesting to compute another statistic, which is the wealth of those top groups, and in particular the oligarchs, relative to total income or total output in the economy, because it gives you a sense of their influence on the economy and also because it gives you a sense of how much revenue there is at stake from taxing their wealth. So let me illustrate. If you get back to the 20 wealthiest people in the country, they have about 2 to 2.2% of total US wealth, and that’s equivalent to about 12–13% of total US GDP.

Okay, so now you’re dividing a stock—their wealth—by a flow. And what it means is that if they spend their wealth—of course, they’re not going to do that in a given year, but imagine that they spent all their wealth in a given year—then they could buy 13% of all the goods and services produced in a given year in the US. So it really gives you a sense of just how big they are relative to the economy as a whole. And also it gives you a sense of what’s at stake with taxing billionaires. Because, of course, the way we think about tax revenue and about government budgets, is often in relation to GDP.

And so here, what you have with billionaire wealth is that there’s a potential tax base; we are not taxing billionaire wealth today, which has been skyrocketing. That’s the flip side of the rise of wealth concentration. The positive aspect in all of that is that now there’s a lot of tax revenue at stake from potentially taxing the wealth of billionaires.

Krugman: Yeah. I mean, my version is, I mean, most people have very little wealth, right? Wealth is highly concentrated, and what most people have is income. But the very top has wealth, and in some sense, the wealth-to-income ratio is telling you how many minions they can buy, how much influence they can buy in the economy and in politics. Is that kind of what you’re saying, or is there something else?

Zucman: No, exactly. When I say that expressing their wealth relative to total income gives a sense of the influence they have, precisely it gives you a sense of how much they can spend on buying media companies, on funding electoral campaigns. Billionaires accounted for nineteen percent of total political spending during the 2024 federal election cycle.

Krugman: Right.

Zucman: They can fund think tanks and foundations, and influence the prevailing ideology like that. So it’s in that sense that it’s really useful, I think, to express their wealth relative to the value of the total income of people in the country.

Krugman: So again, what’s your take on why total wealth has grown faster than income?

Zucman: There are different stories, and I think the one that makes most sense to me and that seems most consistent with the data is that there’s been a number of policy changes since the 1980s that have favored wealth and capital, broadly speaking. So, for instance, you used to have rent controls for housing in many countries; when you lift rent controls, the value of housing wealth tends to go up. Many countries used to have pretty high corporate income tax rates, of almost fifty percent on average at the world level in the 1980s. Well, when the government takes half of the profits of companies, it capitalizes into stock prices; it reduces the market value of companies. But then when governments slash the corporate tax—and it has declined from about 45–50% to about 20–25% today at the global level—well, that again capitalizes into stock prices, and now it boosts the market value of companies, of equities.

And you’ve had deregulation in many sectors that has boosted the profitability of corporations. You’ve had a significant change in the division of value added between labor and capital—the rise of the capital share, the decline in the labor share. That means more profits, more income for shareholders; again, it boosts the value of corporate equity. So all of these changes, they don’t happen like that out of nowhere. They are, of course, heavily influenced by policy.

So, for instance, changes in factor shares—labor and capital shares—have been partly affected by the decline in union power. When unions are stronger, you tend to get a bigger labor share. When unions are weaker, you get a bigger capital share. Also in the way that we organize international economic relations, globalization. When we organize things without any kind of international tax coordination, or to put it differently, if we organize global economic integration by allowing total tax competition—no minimum taxes, no minimum tax rates—then capital owners can threaten to outsource production or to shift profits to low-tax places, and again, it reinforces the power of capital, hence the value of wealth.

Krugman: Okay, But going back maybe twenty-five, thirty years ago—and again, I’ve been in the decrying-inequality business for a long time—we were saying, “You know, there’s a huge rise in income inequality, but it hasn’t really shown up in wealth.” And that really started to change. It’s not just that wealth has increased, but as you say, a huge increase in concentration in a few hands. So, what’s your story? I think I know what your story is about what drives this increasing concentration of wealth, but what is the mechanism? What’s it all about?

Zucman: I think there have been different factors at play, so it’s not just a one-issue story. The thing that seems important to emphasize from my perspective is the dramatic changes that have happened with taxation, particularly in the US. Many people have forgotten, but the US used to have a sharply progressive tax system where capital was heavily taxed, where high incomes were heavily taxed, where large inheritances were heavily taxed. In fact, it probably used to have the most progressive tax system in the world between the 1930s, the New Deal, and the late 1970s. And then during the 1980s, it went all the way in the opposite direction.

And perhaps what’s most striking is what has happened with the income tax. So when Reagan enters the White House in 1981, the top marginal income tax rate in the US is 70%. At the time, it’s the highest top marginal tax rate of all industrialized countries in the world. And then in 1986, you have the big tax reform, the Reagan tax reform, that slashes this top rate to 28%, which at the time was the lowest tax rate among industrialized countries. So it’s a really big change in just five years. And you’ve had that for the income tax, but also for the estate tax. The corporate tax rate used to be 50% after World War II; after the 2018 Trump Tax Cuts and Jobs Act, it’s been reduced to 21%.

And so all of these really big changes, all going in the same direction, have had a massive effect on two things. So, first of all, on the incentives for very wealthy people to try to earn super high incomes. When the top marginal income tax rate was close to 100%—more than 90% in the 1940s and 1950s—there was just no incentive to try to earn a ton of money, because you knew that past some point, almost any extra dollar would go to the IRS. So why bother? Why try to bargain a super high compensation as a CEO? It was just pointless. Now when the top marginal income tax rate is 28%, it becomes really profitable to try to earn super high incomes, right? Because you get to keep most of the money for yourself. So there is this incentive effect.

And there’s of course the pure mechanical effect, which is that with lower tax rates, you have more disposable income when you’re very rich, that you can save and use to grow your wealth. And that’s why I think those changes to taxation, which have been particularly powerful in the US, have played a very important role in the particularly fast rise of US inequality.

Krugman: Now when you talk about incentives, if I were a right-winger, I’d say, “Well, the old system discouraged people from innovating, being job creators, and all that.” And I think that’s not what you mean, right?

Zucman: Well, then it becomes an empirical question, right? In principle, it could be true. You could say, “Well, when people face those super high top marginal income tax rates, it discouraged people from innovating, from launching businesses.” But then you look at the data and you realize that in those decades after World War II, GDP growth was higher, in fact, than it’s been since the 1980s. Investment rates were no lower; in fact, they were higher. US capitalism, broadly speaking, seemed to work okay in that period of time. So of course you don’t know the counterfactual. You don’t know what would have happened if the tax rates had been much lower at the top in those decades. But what you can know as a fact is that these quasi-confiscatory rates on high incomes—and we’re talking about rates that apply to only super high incomes of several millions of today’s dollars—just didn’t kill innovation and growth and capitalism. And you have to think about who you are discouraging, what type of behavior you’re discouraging when you tax very high incomes at very high rates.

Krugman: Right.

Zucman: You could say, okay, perhaps it’s going to discourage innovation, but you know, are scientists or innovators really motivated by the extra income they’re going to be able to make above five million dollars in income? You know, perhaps, perhaps not. You’re also discouraging people who want just to capture rents, who want to create private universities that sell fake diplomas, for instance, or want to exploit patents and squeeze as much money as possible from consumers or patients or sick people, and so on.

So there’s always in the economy people who are motivated by innovating, creating knowledge, and broadly speaking undertaking activities that are positive-sum for the economy as a whole. But there’s also people who are motivated by rent extraction, by different activities that are inherently zero-sum or even negative-sum. And suddenly, when you have 90% top marginal income tax rates, you’re discouraging this type of zero-sum rent extraction, which is the plausible reason why this policy was so effective, at least relatively effective, in the postwar decades.

Krugman: The classic example from my angle has been that corporate CEOs have always basically set their own salaries. But in 1959, extracting a salary that was 500 times that of your average worker just made everybody mad at you, and you didn’t get to keep much of it anyway. And nowadays you do. So…

It looks as if—and certainly from your work and those of us who pick up on it—we have had this process since the late seventies of this concentration, this oligarchy rising in our society, and that taxes have a lot to do with it. So the question is: what are the remedies? I know that we’ll get to wealth taxes in a minute, but we had a workable recipe, which was high corporate taxes, high estate taxes, high top marginal rates. Is there a reason why we can’t just reconstitute that regime, or why we shouldn’t—either as a possibility or desirability?

Zucman: I think we could do it and it would make sense, but also, probably, it wouldn’t be enough. First of all, one of the outcomes of the first Gilded Age at the beginning of the twentieth century was the creation of the progressive income tax in 1913 and the progressive estate tax in 1916. So we instituted taxes to prevent or to curb the rise of concentration that was observed at the time and that many people were worried about.

Krugman: Right.

Zucman: It made a big difference, but also there was, and there’s always been, a kind of fundamental limitation, I think, with this historical experiment, which is that when you’re extremely wealthy—and think about billionaires—it’s, in fact, very easy to own a lot of wealth without having to report any or any significant amount of income. And so it’s, in fact, relatively easy to avoid the income tax. And we kind of knew about that from various anecdotes and case studies.

For instance, a few years ago you had revelations by ProPublica on the taxes paid by US billionaires, and you saw people like Jeff Bezos and Elon Musk in some years reporting very little income, paying very little income tax. There’s even one year when Bezos says, “Look, I’m so poor that I’m going to claim the child tax credit,” and he receives the child tax credit! So we kind of knew about these limitations of the income tax, but it’s only relatively recently that we’ve come to understand that this is a structural feature of income taxation in the US and globally—a structural feature that the super-rich have not yet entered into the system. The income tax is just not the right instrument to tax them.

And so that’s why, in addition to the income tax, you need some kind of tax based on wealth. Because for the very rich, it’s easy to manipulate income to pretend they have no income. So, for instance, Bezos, as CEO of Amazon, didn’t pay himself a wage, he instructed Amazon not to distribute dividends, he didn’t sell shares, and so he didn’t realize capital gains, and so his taxable income was really low. There’s no tax evasion there; it’s all perfectly legal. But, of course, his ability to pay taxes as one of the world’s richest men is, of course, extremely high. And so that’s why, for people like him, the right tax is based not on income, but on wealth, which is much harder to manipulate than income. And that was partly one of the reasons for having an estate tax, which is a tax on wealth, but it’s not enough because the estate tax is just a one-time tax at the time of death. And so you can be in a situation where the wealthiest people in the country, year after year, pay no or almost no income tax. And it’s only when they die—when the estate tax was still functional—that we tried to make them pay a little bit of tax.

That’s the limitation of the US experiment with progressive taxation, which is that it never really tried to make the ultra-wealthy pay personally on an annual basis. And I think that it is this limitation that we need to overcome in the 21st century. And basically, that has to involve some kind of annual taxation based on wealth.

Krugman: Let’s talk about corporate taxes first. We used to collect a substantial amount of corporate taxes. There’s a lot of dispute about exactly who pays them, but your position, as I understand it, is that basically they fall on stockholders. Why did we retreat so much on corporate taxes, and could that be reconstituted or should it be?

Zucman: So first of all, yes, you’re right that the corporate tax used to be a big source of tax revenue for the US. It peaked in the early 1950s at something like six to seven percent of US GDP in tax revenue, just from the corporate tax. That was with a nominal tax rate for the federal corporate tax that was slightly above 50 percent, but the effective rate was also 50 percent. It meant that out of any dollar of profit made, 50 cents went to the government.

Krugman: Right.

Zucman: And today we are down to about 1.5% or so of GDP in tax revenue—1.5 to 2%—from the corporate tax. So it’s a big decline. The standard story is that it’s going to reduce corporate investment, which is going to translate into a decline in the capital stock, and then workers are going to be less productive because capital is good, it complements labor, and so eventually it reduces wages, and so it’s bad for ordinary workers. That’s the standard story, which, frankly, doesn’t have a lot of empirical support for it. But why not? As an intellectual story, it makes some sense in principle.

The other reason, which has been even more powerful in practice, is international tax competition. It’s the idea that we cannot tax corporations at higher rates because otherwise they move to other countries, and that there is this kind of law of nature: the race to the bottom with corporate taxation is something we just have to accept as a law of nature, like gravity. And that also is wrong, because, of course, it’s not a law of nature. It’s a choice that we make collectively to accept international tax competition, or to fight it and to curb it. So I think what this all means is that, of course, we could revert to higher corporate tax rates. That’s definitely something that the US, or in fact any country, can do.

But what I want to say is that, also, it wouldn’t be enough, because the corporate tax is just a flat tax on corporate profits. So someone who owns just one share in Amazon, indirectly is going to pay the same tax rate through the corporate tax as Jeff Bezos, who owns ten percent of Amazon. It’s not progressive, and so that’s why it’s structurally limited.

Krugman: Okay. In the abstract, if our concern is great wealth and we’re looking for some way to limit that and also raise some revenue—though I think in many ways the social and political implications are even more central than the revenue—the history shows remarkably little experience with wealth taxes, right? I mean, we don’t have a lot of evidence, and a lot of people say that they’re unworkable, citing what they claim to have been the history of France. So why don’t you talk to me about the history of wealth taxation?

Zucman: Yeah, I mean, the US never had an annual progressive wealth tax, at least at the federal level. There’s, in fact, a pretty long history of wealth taxation at the state level in the 19th century, with so-called generalized property taxes that were taxes not just on real estate and land, but also on financial assets, typically at flat rates, so not rising with wealth. There’s a long tradition in the US that’s been largely forgotten.

The more relevant history is the European experience with progressive wealth taxation. Many European countries used to have progressive wealth taxes. And I agree that the track record is not good. By and large, they were not big successes. But, of course, there are two ways to look at that experience. You can say, “Well, some countries tried wealth taxes, it didn’t work very well, hence it will never work.” End of story. Or you can try to study this experience and try to understand what were the problems and what lessons can be drawn, and whether the issues can be overcome.

And this is what I’ve been doing with many others in my work, and the conclusion I’ve reached is that, yes, they had issues, these European wealth taxes, but the issues can be fixed.

The biggest issue is that those wealth taxes didn’t even attempt to try to tax billionaires. Look at France, for instance. France is really a striking illustration. The French wealth tax was created in 1981 when a Socialist president comes into power and he has an absolute majority in parliament, and so he creates a wealth tax. But immediately he says, “Okay, we are going to exempt from the wealth tax people who own more than 25% of the shares of a company.” Okay? So if you’re a big shareholder in a company, no matter whether it’s listed on the stock market or not, if you own a ton of stock, that’s going to be removed from the base of the wealth tax. This will be tax-free. But, you know, the wealth of billionaires is precisely that: it’s owning a lot of shares in a company. So what France did in 1981 was like if the US today created a wealth tax and said, “We’re going to exempt Warren Buffett from the wealth tax, or we’re going to exempt Elon Musk from the wealth tax because they have so many shares in their businesses.”

You know, it really makes little sense. And the consequence is that the effective wealth tax rate for French billionaires in 2016, on the eve of the abolition of the wealth tax, was just 0.005% of wealth. They didn’t pay it. And it’s not because they illegally hid assets. No, no, it’s because they were legally exempted from the wealth tax.

Krugman: Why did Mitterrand do that? Do you know?

Zucman: The way the story is often told is that some of the top billionaires complained and went to see him, and they said, “We’re going to move to Switzerland if you do that.” And so that’s how they got that exemption.

But the deeper explanation, I think, is that there was no real commitment on the part of Mitterrand or the Socialist Party to having a tax on billionaire wealth, partly because they thought it would be impossible, that we had to accept international tax competition as a kind of given, that France would be powerless to do anything about that; partly because it was never a big priority for them. They bet on other policies to transform society that didn’t involve progressive taxation, but that involved things like the nationalization of some companies or labor market regulations. But progressive taxation was not part of their ideology, so to speak. They were not very committed to that.

And also, I think in the 1980s, you could make the case that the government revenue at stake was just not very important. So it was not worth fighting for this. I think that was their view. And perhaps you could make that argument in the 1980s or 1990s, but today, it’s impossible. Look at what has happened to the curve—the wealth of billionaires has skyrocketed. So now it becomes really important to include them in the base. So that was the main problem: billionaires were legally exempt.

The other big problem—and it’s related, of course, to the first one—is that those European countries never tried to do anything to fight the risk of out-migration by the super-rich. They just thought that, “Okay, we are powerless. If they want to leave, what can we do?” And that’s just not true. For instance, in the US, there is citizenship-based taxation, meaning if you are a US national, you have to pay taxes in the US no matter where you live. So you can move to Monaco or Switzerland if you want, but you still have to pay federal taxes.

Krugman: Right.

Zucman: France or Germany could have done that; they could have done a variation on that idea. But the big blind spot of the social democratic experiment in Western Europe has been, in my view, this inability to confront the forces of international competition, and international tax competition in particular.

Krugman: So that’s it. Do you want to enlarge on that? Because I think that’s an interesting point.

Zucman: Yeah, these social democratic governments never invested intellectually in trying to organize international economic relations and make those consistent with their ambitions for democratic transformation. Or, to put it differently, the social democratic project was always thought of as a purely domestic endeavor. And when they realized that there was competition from other countries—tax competition in particular—their reaction was not, “What can we do about that? How can we rewrite the rules of global commerce? How can we forge international agreements, or how can we design unilateral policies to protect ourselves from those forces?” Their reaction was not that. Their reaction was, “There’s international competition. We cannot do anything about that. We just have to adapt.” And so we have to embrace the race to the bottom with capital taxation.

And that’s how, in fact, it’s socialist governments, or Labour governments in the UK, or the SPD in Germany, that have slashed the corporate tax rate. Scandinavia, too, moved from a comprehensive income tax where capital and labor are taxed the same, to so-called dual income tax systems where capital income is taxed at lower, flat rates than labor income. Always for the same reason: they never tried to think about how to make social democracy compatible with a globally integrated economy.

Krugman: That makes sense. Although I think that the EU has a kind of minimum VAT rule, right? So the tax that falls on working people, you cannot make it too low, but the tax that falls on billionaires...

Zucman: Yeah, that’s a very good point. The only form of tax harmonization that you have in the EU is on VAT. So when it comes to taxing consumers, the middle class, the poor, all of a sudden we can craft common rules. But when it comes to taxing companies or the rich, what can we do? You know, nothing.

Krugman: So if Ireland goes and poaches corporations—although I think it’s mostly US corporations there, but anyway—Ireland can do that, but they can’t offer shoppers bargains. It’s pretty wild.

Zucman: Yeah, exactly. That’s a very particular worldview, but that’s been central, in fact, in how European construction has proceeded so far. And I think if you want to rationalize this view, deep down there is the idea that it’s not just that international tax competition is a law of nature, but also that it’s a good thing, frankly. That it’s something we should embrace because those welfare states in Western Europe are too big and they need some kind of external outside pressure to force governments to be more efficient—to starve the beast a little bit. And I think many people, even left-of-center people at one point embraced this idea that we should welcome it—it’s going to make us more efficient. We should welcome international tax competition.

And why not? You can make that case, but I think it has two problems. One is that it’s a pretty undemocratic way to decide things. It assumes that voters are going to structurally choose policies that overtax capital or the rich, and hence the need for constitutional constraints or external forces. And, of course, the other problem is that international tax competition, the way that it has unfolded, has fueled the rise of inequality, because the main winners from this are multinational companies and their owners, or people who derive most of their income from capital income, the wealthy, and so on.

Krugman: Right. Sort of Reaganite ideas may have actually had a lot of impact even in Europe.

Zucman: They did. Even though it was never formulated that explicitly, I think this ideology was very influential, in fact.

Krugman: So you’ve been pushing for, in fact, some kind of global accord that basically makes it possible to do more wealth taxation. I’ve been re-reading your G20 paper on all of this. I don’t think this is anything likely to happen anytime soon, but what’s the state of the idea?

Zucman: It will happen, but patience.

Krugman: Yeah, patience. Well...

Zucman: The beginning of all of this was in 2021: there was an agreement among 130 countries for having a minimum tax of 15% on the profits of big multinational companies. And, frankly, very few people had seen that coming, because the prevailing view was, “You know, it’s impossible to get an agreement like that. Small countries like Ireland benefit so much from international tax competition. It’s just utopian.” But it happened in 2021.

And then, in 2024, Brazil had the presidency of the G20, and they wanted to put new ideas on the agenda, and they asked me what I thought. And what I told them is: “Look, I think we should do for billionaires what we’ve been able to do for multinational firms. So let’s try to have an agreement on a minimum annual amount of tax owed by billionaires.” They commissioned a report from me, and some progress was made at the G20, but then, of course, Trump was reelected, so nothing can happen at the moment at the G20 level.

But what’s really interesting is what is happening at the national and, in fact, subnational level these days. Because right after the Brazilian G20 in 2024, the French National Assembly adopted the minimum tax on billionaire wealth that I had proposed. So it’s a tax of 2% on the wealth of people with more than 100 million dollars or euros in net wealth. And it’s a minimum tax, which means that if you already pay an income tax the equivalent of two percent of your wealth or more, you have nothing more to pay. But if you pay less than that, you have to pay the difference to reach the two percent minimum. So it’s the fairest and the most targeted tax that you can imagine, because it’s just on the ultra-wealthy, but not only that, on those among the ultra-wealthy that avoid taxation today.

So France voted for that; it was then blocked by the very conservative Senate. But there is the beginning of an international movement in that direction. You’ve had a bill crafted under French legislation that’s been introduced in Belgium, perhaps soon in the Netherlands, and in Spain. At the moment in the UK, they’re talking a lot about that with the new Prime Minister, Andy Burnham.

And then, of course, most important in my view, is what is happening in California with Prop 40, the California billionaire tax, which is going to be on the ballot in November. This would be a one-time tax of five percent on the wealth of California’s billionaires. Frankly, it’s very important for California, for funding healthcare, Medicaid in particular. But it’s even more important for the US and, in fact, for the world as a whole. Because if California passes the California billionaire tax in November, I think this will really be the beginning of the US and international movement to tax the wealth of the super-rich.

Paul Krugman: Okay. And this is a one-time tax, and it’s retroactive, right? It’s based on your wealth last year.

Zucman: Yeah, exactly. So it has several characteristics. It’s one-time and not annual. And it’s only for billionaires, not for you and me. It’s on billionaires, and it’s on those billionaires who were residents of California as of January 1st of 2026. So it’s too late to avoid the tax, meaning if you were living in California at the beginning of this year, you would still have to pay the tax. So in that sense, there’s a small retroactivity here. And these two characteristics combined—the fact that it’s one-time and based on being a resident as of January 1st of 2026—mean that it’s nearly impossible for any billionaire to avoid the tax by moving to another state. So it also means that if it passes, it’s bound to generate a lot of tax revenue.

The arithmetic is quite simple. The billionaires of California have about two trillion dollars in wealth. So if you tax them at five percent, you get a hundred billion in tax revenue. Another kind of illustration of how big the billionaire wealth tax base has become, which I think is quite striking, is the following: if you look at all the income of Californian people as reported in their tax returns—you know, AGI, adjusted gross income for California as a whole—it is the same number as the wealth of California’s billionaires, 250 people. So, their wealth is 100% of California’s AGI. Meaning, if you have a five percent tax on the wealth of billionaires, it generates as much revenue as a five percent tax on the income of all people in California. So that’s just a very striking illustration of what we were discussing earlier, which is just how massive the wealth of the billionaires has become and hence its implications for public finance.

Krugman: Yeah, one of the things in California is it does have high personal income and high personal wealth, but that’s a few hundred people. They really skew the numbers. And so, how’s it going? I mean, it’s a little bit disappointing to see all of the “don’t be evil” guys from Google and all of that scrambling to protect themselves from taxes. But how are you feeling about the proposition?

Zucman: Well, I’m not surprised by that, right? They have good reasons to hate this, because this is the one tax that they would have to pay. You have to realize that they pay very little today. The billionaires in California pay in income tax the equivalent of just 0.2% of their wealth. So, you know, moving from 0.2% to 5%, even if it’s one-time, it’s a big difference for them, even though their wealth has increased like 200% over the last two years. So from that perspective, it’s a drop in the ocean.

But I think the polling is good. It’s going to be a battle just because the billionaires are spending tens of millions, hundreds of millions already, to stoke fears and try to defeat the proposition on the ballot. But I think the logic, frankly, is so compelling, and also billionaires are not very popular at the moment in California, like everywhere else, so I think it has a good chance to pass.

But what I want to say is that, first of all, it’s important for California because there’s a big shortfall of federal funding for healthcare as a result of the One Big Beautiful Bill Act. And so California needs to find broadly a hundred billion in revenues to just preserve Medicaid. So that was the main reason for having this on the ballot in the first place. And so if it doesn’t pass, you’re going to see the number of uninsured people rise a lot in California. Under business as usual, it’s going to increase from six percent to ten percent. So that’s why it’s important.

But more fundamentally, in my view, it’s important because it’s the one concrete measure that can begin to make a difference to oligarchic wealth and power.

And don’t get me wrong, five percent one-time is not enough, but this is what’s going to pave the way, I think, for eventually some kind of federal wealth tax and federal annual wealth tax. And the reason why there’s good reason to view it like that is because this is what happened for the income tax at the beginning of the 20th century, which was first implemented by a number of states, like Wisconsin in 1911, before becoming federal policy in 1913. So that’s why it’s really important. And I can tell you that the whole world is watching California. I think people in France are like, “This is amazing! Go California, tax the billionaires!” And this is going to be a blueprint for what we’ll do in France, in the rest of Europe, and frankly, globally.

Krugman: States as laboratories of anti-oligarchy. Let’s hope for the best. Thanks a lot, and onward with the project. Take care.

Zucman: Thank you so much, Paul.

I omitted the Markdown creating a link on the words “still ‘coming soon’” for clarity, to emphasize only the problematic link in my original prose. (Also, it’s fun to use emoji as named link definitions, like in this example.) ↩︎︎
I of course reported this to the developer of Banish, twice, but he never responded. I, err, banished Banish from my own devices, and upon finishing this article, I’m going to update my 2022 recommendation of Banish to un-recommend it. ↩︎

I bought my wooden boxes back when they were $35. I don't know if I'll keep buying them now that they're $50: ↩︎
AirPods work flawlessly because they're cheating with a proprietary Apple-only protocol. ↩︎

This is the second half of the fourth part (I, IIa, IIb, III, IVa) of our honestly-who-knows-how-many part series laying out some general guidelines for how pre-modern armies are organized. Last week we took a look at how the leadership of these armies was drawn from the existing elite classes of their societies. As with other factors, armies cannot help but recreate their civilian social structures on the battlefield, with the result that the military leadership class often mirrored, where it wasn’t simply identical with, the civilian ruling class.

Now it will not surprise you that pre-modern military literature, written almost entirely by elites in the leadership class for other elites in the leadership class, is very interested in leadership and tends to attribute all military success or failure to the fellows in charge. Modern military science, however, has increasingly recognized the importance of combat motivation in individual rank-and-file soldiers.¹

As noted last time, we can break this broader concept of combat motivation into two parts: morale and cohesion, where morale is the soldier’s attachment to the cause and belief in its possible achievement and cohesion is a soldier’s attachment to his fellows. What combat motivation studies have tended to show is that morale will get a soldier to the battlefield, but will not keep him on it; it is cohesion instead, the ability of a unit to stay together under pressure that is essential for enduring the terror of combat.

That said, different armies and different societies generate cohesion in different ways, as we’ll see. Now this is one component of this series that is a bit of an exception: so far I’ve been hammering that most societies are going to be pushed very strongly towards specific kinds of recruitment, organization and leadership as a result of their civilian organization. Meanwhile, as we’ll see, certain kinds of cohesion depend to a greater or lesser degree on specific social structures or assumptions, but it is a lot more common to see armies that simply have poor cohesion due to a mismatch of cohesive principles and military or social structures.

But first, as always, recruiting and maintaining large pre-modern armies is expensive! Much like many of those pre-modern armies, this project is supported by devolving the costs of my ruinous book-buying habit on to ~~recruits~~ readers. You can help by spreading the word to new readers and by supporting this project over at Patreon. If you want updates whenever a new post appears or want to hear my more bite-sized musings on history, security affairs and current events, you can follow me on Bluesky (@bretdevereaux.bsky.social). I am also active on Threads (bretdevereaux) and maintain a de minimis presence on Twitter (@bretdevereaux).

The Nature of Cohesion

We’ve talked about cohesion a few times here, so before getting into the systems that can generate cohesion, we can be fairly brief on what cohesion is. As the word implies, cohesion is the ability of a unit to hold together under pressure, but this is one of those concepts with a simple definition but more complex application.

On the one hand, cohesion is one of those ‘harder said than done’ principles. When a group of any animals is subjected to peril, the instinct is to flee and for humans, who are not herd animals, the instinct is to scatter, to flee individually. The goal of cohesion is instead to have individuals respond to peril by seeking the safety of the group rather than the safety of individual flight, so that intense fear causes the group to solidify rather than disperse. That is, as we’ll see, a challenging-but-not-impossible emotional response to stimulate, as humans are pack animals. That said, it has to be an emotional response, something sub-rational, because it needs to functions in conditions of intense fear where rational thinking is ineffective.

So you can think of cohesion, in its simplest form, as a kind of social or mental conditioning that aims to alter individual’s fear response from, ‘split up for safety’ to ‘group up for safety’ at an emotional, sub-rational level.

And then on the other hand, that has complex implications for battlefields in which humans generally fight as units rather than as individuals. Not all humans fight this way, I should note: warriors in a ‘first system’ ‘pounce-and-flee’ warfare system – as we see with hunter gatherers or early agriculturalists – often fight in a far more atomized, skirmishing style with no regular formations and no expectation that individuals will hold their ground or cohere under pressure. Instead, warriors in such a system can fall back and regroup relatively freely. But complex agrarian (even non-state complex agrarian) and pastoralist armies do fight as larger units, with complex group tactics that demand individual combatants work together and stick together much more tightly.

Meanwhile, if the unit remains cohesive – if the individual men remain bound together as a single mass – then their leaders can more readily maneuver the whole mass into action. After all, if the presence of peril is psychologically pushing each soldier to cohere for collective safety, then an officer can use that cohesion to push the group as a unit, potentially even moving it into greater peril. This is the foundation of all shock tactics – at least, all of them involving an even remotely equal opponent – because delivering ‘shock’ (that is, advancing into close combat in a group) demands advancing into peril, which is a think that is normally psychologically quite hard to do. As Ardant du Picq notes, “Man does not enter battle to fight, but for victory. He does everything that he can to avoid the first and obtain the second.” Getting fellows to walk into range of an opponent’s spears (potentially walking through the range of their slings, bows or muskets to do so) requires moving directly against human psychology. But if the whole mass of men coheres, the mass may be moved forward: group psychology succeeds where individual psychology would fail.

Of course cohesion is equally relevant – for the same reasons – for getting men to stand under fire, either in a tight formation or in more dispersed skirmish order (as in modern warfare). Once again, the normal human response to being in a ‘zone of danger’ is to leave it, so the cohesion response is required to get men to stay in the ‘zone of danger’ – the unit is in the zone, the men have cohered to the unit, so the men remain because the unit remains. Now, absolutely there are a small number of people in any group who have the right psychological mixture to do these things alone, but armies cannot be built out of a tiny handful of saints and sociopaths, they must be built out of regular men.

So cohesion serves several related purposes on the battlefield: it keeps men from fleeing but it is also the means by which they can be pushed into offensive action, which is to say it both keeps them from fleeing but also gets them fighting, all as a product of the action of holding them together. Even if a unit must withdraw, cohesion allows them to withdraw as a unit – maintaining fighting capability (which in turn deters an enemy from pursuing too aggressively) – rather than breaking apart into a rout (which an enemy can pursue aggressively).

So how does cohesion happen? High cohesion is most often the product of tight bonds between the men in a unit, though those bonds can be achieved in a range of ways. That said, as we’ll see, certain ways of producing cohesion can also produce a kind of corporate cohesion, where the cohesive principle ends up rooted in the identity of the soldiers (which they share), which creates a kind of cohesion that persists even when soldiers do not necessarily know their fellows (but when they do know that their fellows are also soldiers and so share the same formative, cohesion-building experiences; that’s why I frame it as ‘corporate’ in nature).

So cohesion is important, but it is also fundamentally unnatural: it must be produced somehow, it cannot be assumed. In practice there are two ways (or categories of ways) to produce cohesion: it can be produced in civilian society or it can be produced ‘in the ranks.’

Cohesion Dyed in the Wool

One way to achieve strong cohesion is to have it produced organically through civilian society. Tight social bonds are the key mechanism for producing this kind of cohesion: it derives from serving and fighting next to men who you know well in peace time and who will continue to know you well after the fight is done. The social pressure not to let these fellows down – fellows you will have to live with long after the smoke clears – is one of the few pressures that is as strong as the fear of dying. Or, as I sometimes put it, the one thing humans might fear more than death is shame. But for shame to work, it has to come from a peer group the individual will have to live with.

In practice, this kind of cohesion then tends to come one of two ways: from a small community or from a small, tight-knit group within the community.

The classic example of the former case are various forms of civic militias, like Greek hoplites. The hoplite phalanx of a Greek polis was generally divided into sub-units by tribe or neighborhood (phyle or deme) so that men served next to their friends, neighbors and family members in the phalanx as it was drawn up. Of course in some poleis, this sort of closeness was institutionalized through common dining groups, but it seems pretty likely that regular social dining with the men who would be near you in the phalanx was common across Greek poleis. Consequently, when a hoplite stood in the ranks, he knew he was being observed by everyone (at least, all of the men – though he could be assured his mother, wife and children would hear of his conduct too!) in the world who mattered to him.

Via Wikimedia Commons, an arming scene showing hoplites and a young man being armed as a hoplite (c. 530-510 BC). Although hoplites had little formal training or drill, they were often highly cohesive on the field because their cohesion was organic rather than trained.

The result is the creation of what is termed in military science a primary group: the small, face-to-face social group around a soldier, which tends to be tight and cohesive. Instead of generating that group ‘in the ranks’ – impossible for an amateur militia force that only formed up when there was a battle to fight – these sort of citizen militias instead form the primary group during peacetime and then use it as a basic building block in wartime to achieve that cohesion. As a result, a civic militia like a hoplite militia could be cohesive despite having little or no formal training or collective drill and relatively little in the way of command and control structures. Their cohesion was organic, derived from underlying social structures, rather than needing to be intentionally manufactured through training.

The alternative for ‘organic’ cohesion is the creation of a smaller unit of society that is similarly cohesive, often in the context of a much larger (and thus more anonymous) society which struggles with the kind of ‘small town’ cohesion of the Greek polis. This, of course, is generally the cohesion of a warrior class: the overall society may not be small enough for everyone to know everyone else well enough to generate that kind of tight social pressure, but the warrior-class might be. The aristocracy broadly construed, for instance, of even a large medieval European kingdom might consist of only around a thousand or so households. The kingdom might not be organically cohesive, but the aristocracy could be – though as we will see, knightly cohesion was reinforced through training and drill as well. One of the most striking examples of this kind of cohesion in action to me has always been the performance of the English huscarls at Hastings (1066): even as the rest of the army crumbled and the battle was lost, this group of vocational warriors held together, despite tremendous pressure.

Via Wikipedia, part of the Bayeux Tapestry (c. 1070s), showing the last stand of the English huscarls at the Battle of Hastings (1066). Even under tremendous pressure (arrow volleys and cavalry charges), the huscarls remained cohesive. The main levy force (the *fyrd*), however, did not, breaking up and leaving the huscarls isolated on the field where they were defeated.

Hopefully, you are also beginning to see how some of what we’ve laid out in these posts can ‘line up’ to produce strong military systems. A civic militia, for instance, can benefit greatly from these tight social bonds: in the ranks, everyone knows everyone else and the unit is led by elected officers who are the same men who lead the community in peacetime. The whole unit can thus draw on the familiarity and strong social bonds without needing to build those connections from scratch. The same, of course, goes for the retinue of a Big Man, whose retainers all know each other (and will continue to do so after the battle because they’re all socially connected) and who all know and already respect the authority of the Big Man who commands.

Now there is another requirement to making this kind of cohesion work effectively: there has to be important social value placed on military performance. For the militia man in a medieval schuttersgilde or a Greek hoplite or a knight riding out in his lord’s retinue, fighting bravely was crucial to their status in the community. Their friends, family and neighbors would be watching and would care if they stuck together or ran away. But for that to work there has to be some status for these men attached to the performance of military service.

A village can have very close-knit social bonds, but if the peasants living there don’t consider the role in society to be fighting, don’t value military service and don’t see themselves as personally involved in the wars of their rentier-elites, it will be almost impossible for those rentier-elites to actually harness the latent social cohesion of the village. Those villagers won’t hold together under pressure on the battlefield, they’ll scatter together – their social cohesion will be addressed in the ways they find socially valuable (like supporting each other with food during hard times). One common ‘failure state’ of military organization is where a political leader raises a population expecting to get organic cohesion but – because the society has not invested the social value in the fighting that those kinds of people do (so they may value knightly warfare but not the infantry warfare of peasants, for instance) – the cohesion simply isn’t there and the force collapses when put under strain. Levies drawn from the underclasses of a society – peasants swiftly formed into a local militia, for instance – often collapse this way under pressure, because the society at large (which is to say, the elites) have not dedicated the social value or resources to build organic cohesion.

In addition, this kind of organic social cohesion is very hard to ‘scale up’ since it relies on relatively small-scale tight-knit social bonds. One solution, however, was for large states to recruit the component units of their armies from specific locales, in what is termed a regimental system. Under a regimental system, soldiers do not move from one unit to another but rather are raised and spend their entire service career (which may be short-service or long-service) in a single unit. Often, when this system was combined with volunteer or short-service units (as in, for instance, the American Civil War or the British army in the First World War), units were intentionally raised from small geographic areas: individual states, cities, towns and so on. While the regimental system itself is a modern phenomenon, similar sorts of systems existed earlier; the Roman socii system seems to have functioned on a similar basis: Roman socii stayed in units recruited from their relatively small communities.

A larger army can thus try to harness some of that local cohesion by recruiting local units and keeping them intact, although this also creates organizational challenges: those soldiers are unlikely to be as willing to serve outside of their original units. They was told, you see, that they’d be serving with the 2nd Maine and the 2nd Maine only. That can cause issues if the original unit has been attritted so badly that it is no longer really functional (but cannot readily be merged with others), but also could create problems because it could also geographically concentrate casualties. The famous, grim example of this was the 11th Battalion of the East Lancashire Regiment (the Accrington Pals), all recruited from the same town, suffered 80% casualties in just thirty minutes of fighting at the Somme (Jul. 1, 1916), practically obliterating an entire generation of the town.² The British abandoned the recruiting of ‘Pals Battalions’ after the Somme in no small part for that reason.

However, as you might be picking up, not every society generates strong enough organic cohesion to orient a military around (or the ‘warrior class’ that does is too small to form the bulk of the military). So then the question becomes how to create cohesion.

Training Cohesion

And it turns out it is possible to train cohesion into a unit.

What is striking is that historical societies talk about this process using a range of different understandings for how exactly they are inculcating bravery through training. Greek and Roman writers often frame this sort of training not necessarily as teaching soldiers specific, coordinated motions (the swinging of a sword, the throwing of a javelin), even though we know that the Romans, at least, did drill that sort of thing, but rather as rendering soldiers inured from hardship by putting them through hardship, by having them undertake strenuous duty regularly with strict punishments for failure (and generous rewards for success).

By contrast, early modern European drill, though it equally involved a lot of strenuous work, was understood more at the time as trying to produce a ‘mechanical soldier.’ The early modern European aristocrat largely concluded that the raw lower-class clay he was forced to work with for his army was temperamentally unsuited for bravery (these fellows were mostly stuck up snobs) and so could only be made brave by having the necessary actions for battle – loading and firing firearms, moving in formation – drilled over and over again until they became mechanical muscle memory. They use the same methods as the Romans – repetitive training of basic actions under as realistic circumstances as possible, with strict punishments for failures of discipline – but understood the mechanism of action to be quite different.

Now I want to be clear here what I mean when I say drill. Drill in this context is training through strenuous repetition of simple actions in preparation for combat. Not every army drills! There’s also a distinction here between armies that value “collective synchronized discipline” – the ability of soldiers to move together in synchronized action – and armies that don’t (you can use muskets in collective, synchronized musket lines but you can also use them independently in skirmish formations, for instance).³ It is likewise possible for armies to insist on physical conditioning in ways that do not produce group psychology effects, the difference between training together and training individually.

Via Wikipedia, an illustration of a Ming musket drill using volley fire techniques (1639). Drill and synchronized discipline were not purely a phenomenon of Europe or the broader Mediterranean, they appear in East Asia quite frequently as well. While it is easiest to illustrate this with musket drill (as above), synchronized discipline in China goes back at least to the Warring States period (475-221 BC) and in Japan we have plenty of evidence for synchronized discipline for infantry using various polearms before the large-scale introduction of firearms during the Sengoku period (1467-1600).

Now to be clear, obviously rigorously drilling soldiers in the manipulation of weapons is going to train what we can call ‘skill at arms’ – the effective manipulation of complex weapon systems – but we’re interested in the psychological conditioning here.

And the way modern thinking understands this same process is rather different than either ancient or early modern aristocratic thinking, in part because modern researchers and scholars have bothered to occasionally ask common soldiers about it. While the concept of unit cohesion has existed, I’d argue, since antiquity, it really only started receiving really systematic study after the Second World War, with the main conclusion of those early studies being that unit performance was heavily sensitive to the tight bonds in small units. Which is to say soldiers were motivated to fight for their ‘buddies’ at the squad, platoon and company level and that this social bonding effect was the primary source of unit cohesion.

The question, of course, was how a military went about manufacturing those sorts of social bonds so that units cohered under pressure. But of course the military wasn’t approaching these questions with a blank slate: in many ways the western military tradition (hardly alone) had already developed a system for manufacturing unit cohesion – what it was coming to realize is that it had never really understood how that mechanism functioned.

Instead, while the role of drill in training specific skills is important, it also imposed upon each batch of recruits intense conditions of shared suffering combined with creating a barrier to entry into the final group (one had to endure the initial drill and training process). In short, taking a bunch of potential soldiers and throwing them all into the same difficult situation (physical training and drill) they have to overcome together over an extended period of time (weeks or months, if not longer) is a way to ‘speed run’ the social bonding process to create a strong, cohesive unit.

One of the risks this approach is thought to run, however, is that rotation or high casualties can erode that cohesion. The soldier has cohered, after all, to a ‘primary group’ consisting of the men he trained or served long-term with, but that bond can be ruptured as members of the primary group are killed or rotated out of the unit (or the soldier is rotated into a new unit where they don’t know anyone). One of the responses to this reality is to avoid individual soldier rotations (such rotations in the Vietnam War were famously blamed for low morale and discipline) and instead rotate whole units, but of course there is nothing doing about casualties and the need to replace them.

The thing is, while certainly some units suffer reduced cohesion and thus reduced combat performance as they take casualties and – in the accidentally memorably bloodless phrasing of one of my graduate school colleagues – “the primary group disintegrates” that also quite clearly doesn’t happen to every military. It is a bit of a grim (and very modern) example, but the Wehrmacht (the German army) in WWII remained cohesive despite absolutely staggering casualties by war’s end and the effective impossibility of maintaining meaningful primary groups in the face of those losses.

In a similar vein, new assignments or distant posts often seem substantially less disruptive on cohesion in long-service professional forces. And indeed, mercenaries and long-service professionals can show remarkable cohesion under strain, even when the men in question haven’t necessarily been trained together. Xenophon’s Ten Thousand, recorded in his Anabasis, provide a notable example of this: the Ten Thousand were a mercenary force composed of men from ten different smaller mercenary units, scattered over the Greek world and in most cases we have to imagine the men who joined were not joining together with their neighbors but as deracinated mercenaries. Yet the Ten Thousand show extraordinarily strong cohesion under pressure, both in pitched battles but also under the steady strain of a long march under continuous threat.

That sort of ‘plug and play’ cohesion also shows up in long-service professional armies as well as other kinds of armies that have simply been in the field for a long time as the result of very long wars. One can see it, to take a modern example, quite clearly in the performance – in both victory and defeat – of British regular troops during the Anglo-Zulu War. At Isandhlwana (Jan 22, 1879), a British column was effectively annihilated when enveloped by a larger Zulu force but most of the regulars remained cohesive to the end even when it was clear the battle was lost. The same intense cohesion among the regulars enabled an unlikely victory the next day at Rorke’s Drift (Jan 22-3, 1879) when a badly outnumbered garrison post held off a large Zulu attack. Of course we should also note the remarkable cohesion of the Zulu (in their case a mix of organic cohesion and cohesion developed over frequent campaigns) in these battles, where they were able to persist on the attack despite shockingly heavy casualties.

Via Wikipedia, a 1880 painting by Alphonse de Neuville depicting (in somewhat dramatic form) the Battle of Rorke’s Drift (1879). As an aside, I generally stick to period artwork on the blog whenever I can, but of course we should be alert to the fact that even period artworks **are not photographs**. So the composition of this painting, clearly intended to highlight the heroism of the British is deliberate and in a way we might say ‘more real than real’ (for instance, it appears to combine several actions at once that happened over extended periods and exploits the use of foreground and background to render the Zulus into a dehumanized horde rather than more human opponents). We must read our images – even period images – just as critically as we read our texts and this is no less true for the above pictures of hoplites or the Bayeux Tapestry as it is for this modern painting.

What I think is going on here is that over time these fellows are being bound not only to a primary group, but also a corporate, professional identity, effectively a professional version of the corporate identity of the ‘warrior class’ discussed above. On the one hand, all of these ‘old soldiers’ still have shared experiences, because even though they were not drilled together, they were all drilled the same way and they all ‘know their business’ the same way. At the same time, they have a common connection to a shared identity nonetheless: they’re all soldiers, not merely by circumstance but by identity. Being a soldier is not something that has happened to them, but something that is part of them. And of course those elements – difficulty of entry, commonalities in experience in the group, a shared sense of belonging – are all elements that encourage group cohesion.

Now again, in both cases, the actual mechanism for producing this psychological and social bonding effect is drill and discipline, which of course also have other effects (as all training does) and are often done for those other purposes, developing cohesion as an accidental (but very necessary) byproduct.

Now as you might gather, the research on training and unit cohesion is, at this point, voluminous; this can only have been an overview. But I think, at least for thinking about worldbuilding (and also a general framework in which to understand the specialist literature), thinking in terms of two categories of ‘manufactured’ cohesion – primary group cohesion (a result of a group being trained together and undergoing hardship together) and corporate identity cohesion (a result of a shared sense of professional or corporate identity among a much larger group, married to shared experiences of training and hardship). However remember: your subjects may view the matter quite differently, understanding the improved combat performance to be the product of something other than the psychological conditioning that modern research focuses on.

Cohesion and its Absence

That leaves us with really four major avenues for a unit to develop effective cohesion: the organic cohesion of small communities (up to the level of a small town, but not generally much larger), the organic cohesion of selective groups (like warrior classes or specific guilds or social clubs) with in a larger, less cohesive society, manufactured primary group cohesion that results from training a unit together and having them endure hardship together and manufactured corporate identity cohesion, a result of a shared sense of identity among a larger group that have a sense of shared hardship.

Note, of course, that there’s no reason these mechanisms for cohesion cannot be combined. Roman citizen armies in the Middle Republic were recruiting with at least some substantial organic cohesion from the citizen class (and the socii in their even smaller, potentially more cohesive groups), which was then reinforced by strict discipline and the experience of military life, effectively layering small community cohesion on top of manufactured primary group cohesion. Likewise, a medieval knight (or other mounted warrior) is already coming with the organic cohesion of a warrior class, but knights also trained together extensively in small units (the conroi, a unit anywhere from a half-dozen to couple-dozen mounted warriors) and would fight in battle as part of that unit, layering that primary group cohesion over top that warrior class cohesion.

The thing is military units are not always cohesive. This is a bit of a difference from the previous sections in this series. Military units, after all, that exist presumably have to have been recruited, supplied, organized and paid somehow or they wouldn’t exist. But there’s no reason a society cannot form up an army or a unit within an army that simply never coheres will and as a result performs poorly on the battlefield. Indeed, we’ve discussed both fictional and real world examples of poor cohesion or combat motivation in the past.

Now the student of history generally comes at these questions knowing the outcome: we typically know that an army either collapsed under pressure or cohered under pressure and are seeking to understand why. Each society’s system for generating cohesion is going to differ in some respects – indeed, you may well have different cohesive principles at play in different parts of the same army for different units raised differently – but a basic sense of the varying ways that cohesion can be generated can help one begin to work out why this or that historical army might have performed well or poorly, creating hypotheses to then investigate more closely in the evidence.

For worldbuilders, the task is somewhat inverted because the armies are fictional and their battles yet unfought. So instead the task is thinking about the societies one has built and the ways they could generate cohesion and giving them military and social institutions to match. Or, crucially, giving them military performance to match. So if your story is meant to feature a fearless, highly effective sort of army, you probably ought to think at least a bit about why they cohere together so well (and not think about it in just bland ‘because they’re super soldiers’ way). Alternately, if you want a military to surprisingly underform, think about flaws or weaknesses in its cohesion – perhaps the a Big Evil who hasn’t given enough thought to psychology or has simply assumed that he can rely on organic cohesion without having done anything to foster it, for instance.

Perhaps most importantly, remember that cohesion is a properly of the regular soldiers of an army, rather than their leaders. Highly effective armies combine capable leadership with high degrees of cohesion. But cohesion can turn against leaders as well – after all, a unit that has strong group bonds will be cohesive when facing the enemy, but it will also be cohesive in a mutiny.⁴

We’ll probably have a shorter fireside post next week, but after that, we’ll close out this series looking at some real and fictional examples of how all of these elements – civilian society, recruitment, supplies, organization, cohesion, leader and so on – fit together to make coherent military systems (or in some fictional examples, incoherent ones).