Economics of Warfare: Why Do Soldiers Fight?

Edward L. Glaeser is an economist at Harvard.

During this holiday season, it is nice to take a break from the bleak economic news and think about other times and places.

Personally, I’ve been escaping into the even bleaker world of Civil War battlefields and prison camps. My co-author and friend, Matthew Kahn, and his wife, the economic historian Dora Costa, have written a book on the Civil War entitled “Cowards and Heroes: The Social Face of War.” In the hands of Ms. Costa and Mr. Kahn, economics can help make sense of the war and teach us something about the importance of social capital, the ties that connect each of us with the rest of humanity.

While Ms. Costa and Mr. Kahn break plenty of new ground in their study of the Civil War, they are following a 50-year tradition of economic historians studying slavery. For example, Ms. Costa’s mentor, Robert Fogel, earned a Nobel Prize in part for his work with the historian Stanley Engerman, concluding that slavery was an economically viable institution. Mr. Engerman and Mr. Fogel were not defending the horrors of human enslavement, but rather refuting the hypothesis of earlier, more pro-South historians: that slavery would have disappeared on its own.

Still, even if emancipation wouldn’t have happened on its own, the very fact of the war still presents a great puzzle to anyone who likes to think that humans have some degree of rationality. Statesmen in the 1840s suggested ending slavery with a negotiated settlement, sharing the costs of emancipation between Northerners, Southerners and the slaves themselves, who would work to pay off their share over a number of years. While rationality should have made this type of bargain more attractive than the horrors of war, hard-liners dominated debate on both Northern and Southern sides in the 1850s and the result was the death of 620,000 soldiers.

Ms. Costa and Mr. Kahn’s analysis starts after the gunfire at Fort Sumter, S.C., and they address one of the most important questions in warfare: Why are soldiers willing to fight?

Warfare presents a paradox. War is perhaps mankind’s most awful activity but also where we see the most generous acts of self-sacrifice. In the Civil War, men went to fight singing “as he died to make men holy, let us die to make men free.” Over the holidays, many will remember that our soldiers are still risking death to protect the rest of us.

Ms. Costa and Mr. Kahn are not the first writers to try and understand why soldiers fight.

The military historian, John Keegan, argued forcefully that soldiers fight for their mates, to honor the bonds of friendship formed in small military groups.

The Civil War historian James McPherson (whose class I took 24 years ago), addressed the subject in a beautiful book looking at the letters and diaries of Civil War soldiers. Mr. McPherson’s literary evidence supports Mr. Keegan’s view but also shows the importance of other motives, like a profound belief in the injustice of slavery.

Ms. Costa and Mr. Kahn are economists who use data, not diaries, to assess men’s motives. They use enlistment records, desertion records and survival records from the Andersonville prison camp. They do find support for the importance of abolitionist ideology. People from counties that voted heavily for Abraham Lincoln in 1860 were less likely to desert and more likely to enlist in the first place. They also find that farmers and Germans were less likely to run away. Artisans and people born in Britain and Ireland were more likely to desert.

Yet their data particularly supports Mr. Keegan’s claims about the importance of social connection. Companies with homogeneous soldiers, made up of ethnically similar people and drawn from geographically proximate areas, had desertion rates that were half as large as more diverse companies. Homogeneity also had large effects on African-American companies, which had much higher desertion rates when they were drawn from far-flung places.

Social capital — connections between soldiers — led them to keep fighting, for they were fighting for each other as much as for any abstract cause. Social capital also led to fewer deaths in the Andersonville prison camp. Friends were crucial for surviving that hell hole. For example, the survival probability of an Irish or German prisoner increases by as much as 20 percent, when that soldier had a greater number of fellow Irish or German soldiers in his company in the camp. Prisoners were also more likely to survive when the prison contained other people from his town.

Ms. Costa and Mr. Kahn’s work reminds us that diversity has had costs as well as benefits. Sadly, in many settings, people are more likely to behave badly toward people who are different from themselves. Ms. Costa and Mr. Kahn cite an experiment of mine involving trust and cheating, where Harvard undergraduates were far more likely to cheat fellow students who had a different country of origin.

These results don’t mean that the difficulties of diversity cannot be reduced. Modern military training is quite capable of forging a common group identity among initially diverse soldiers. The election of Barack Obama as president clearly indicates that once seemingly insurmountable social barriers can be overcome.

Ms. Costa and Mr. Kahn’s book illustrates the importance of social connections, an important topic during this season. Our friends and family make holidays more joyful, and they can also be a lifeline during more troubled times. That is all the more reason to spend the holidays strengthening our ties to the people that we love.

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As a veteran who served for 21 years and was in several wars, I would like to point out that there are a variety of psychological layers to the reasons that men, and now women, fight in wars. Both the dimension of group identity in terms of what the military calls the mission (peacekeeping, freeing a country from dictatorship, etc) and unit bonding not only exist but are two interlocking and associated factors. But I would like to mention that outrside social group identification (i.e. pre-military), a bit contrary to what you are hypothesizing, somewhat dissolves when the group identification becomes the unit and the mission. I don’t think people credit the military enough as a strong socialization force, for example, in breaking down racial and other socio-economic barriers, esp once the unit goes past training to a war zone and soldiers have to depend on each other for their lives.


The generals and planners talk about fighting forces and something they call the ‘tooth to tail’ ratio. Those are the same guys that like to talk about defending freedom, motherhood, and apple-pie. They also like to tell folks that there is glory and honor in battle. Maybe they’re right, and I just missed it.

The guys I hung out with were more affiliated with the ‘tooth’ part of the war-machinery. Anyways, when the day was done; and even if it was a particularly bad day, no-one ever talked about the glorious causes mentioned by the REMFs. Mostly they didn’t talk at all. If you paid attention and looked closely at their eyes you could catch a hint of what was going on though. You might catch a look that said, “Man, I can’t believe you did that.” Deep down, you knew he’d have done the same though.

Sometimes a guy would say, “You dumb MFer, why did you do that?” He’d mean every word of it. But at the same time he knew he wouldn’t be there except for that, and he’d have done it too.

Sometimes the look would say, “Man, I screwed up and somebody paid or could have paid – big time.” The nod or shrug of response at least said, “I understand.” and usually would even forgive.

You see; way out there on the jagged edge of combat – where tooth clashes with tooth, the men know the truth. The REMFs are lying. It’s about keeping your buddy alive, and how that plays into your survival. Nothing more. The really accomplished Generals know this and they use it to achieve their aims. They put a group of soldiers in a situation where protecting each other takes and holds a chunk of ground, gets a body count, or over-runs a defensive fortification. They then move a marker on a model or write something on a map or in a book and head for the officer’s club where they drink a toast to the glory and honor of war.

Meanwhile, hours, days, weeks, or decades later; what I call the ‘three beasts’ often show up to do their grotesque dance. Look deep into the gaze of an old soldier and you will see them there. They’re always together and they’re always the same ones: sorrow, joy, and guilt. They dance, vying to lead, every time he thinks of that time and he never knows which one will emerge to call the tune or which one will be left to pay the fiddler.

There is sorrow for his closest friend or the trooper he hardly knew; who was badly maimed or had his life jerked from him, sometimes quickly, and sometimes in the most horrible way.

There is joy, because it wasn’t him.

There is always plenty of guilt. Guilt, because it could have been him. Guilt, because he’s happy it wasn’t him. Guilt, because he might have done something different. Guilt, because he might be squandering the reason the God left him and took the other guy.

In any event; glory, honor, heroism, patriotism, and any of the other platitudes never show up for the dance. It’s probably for the best, as the beasts would chase them away.

© 2002 Ed Boysun

“Modern military training is quite capable of forging a common group identity among initially diverse soldiers. ”

like what?

– What the f#@! are you even doing here?
– Sir, I got lost on the way to college, sir.

— Jarhead, 2005

I say it could be Harvard, or Yale.

Some of the factors that you use as reasons that may answer the question, “Why Do Soldiers Fight” are so obviously off the mark that it makes one wonder if you are anywhere near providing an answer(s) to this question. One could conclude that your analysis is often “Northcentric” and therefore does not supply answers to the overall phenomenon.

For example, you mention “acts of self-sacrifice” and buttress this reason with the Battle Hymn of the Republic (let us die to make men free), which by-the-way was not written until the Civil War had already started. Later you list the importance of a profound belief in the injustice of slavery and the importance of abolitionist belief.

While these may indeed be lofty sentiments, I hardly think these “reasons” were shared by Southern soldiers (who fought with equal vigor), and therefore they do not provide insight as to why soldiers fight whatever side, country, tribe etc. they may be on. I am reminded of a Civil War documentary wherein a southern soldier, too poor to own slaves, was asked why he fought and he replied, “Because this is my land and you’re on it”

Your “social capital” analysis bears more fruit, but here again only marginally. The U.S. military abandoned fighting units comprised of geographically homogenous soldiers because communities could find their male population wiped out if their unit was destroyed (think Pickett’s charge at Gettysburg etc.).

No evidence is given to the extent to which modern military training can forge a group identity from initially diverse soldiers that withstands extreme pressure. Again, I am reminded of the very credible fighting effort of the Austrian-Hungarian Empire during World War I -a military that was comprised of many different ethnic groups that often disliked each other. An analysis of their fighting spirit might provide more insight into the relevancy of “social capital” as a basic reason to fight, for I can think of few other examples where a diverse military faced such desperate conditions where the outcome would determine the very existence of the country.

As it stands, I find that some of the arguments given in this article do not explain why soldiers fight and indeed sometimes even undermine the attempt to offer an explanation. Personally, I think that an analysis of interpersonal relations at the squad level may bear more fruit (call it “squad capital”), rather than lofty ideals that are quickly forgotten when a bullet flies by your head. Which goes right to your conclusion of strengthening our family (squad) ties at important holidays such as Thanksgiving, Christmas etc.

Contrary to popular belief, few if any, go to war because they”love thier country”.More important motivation is hate rather than love. They may hate their job, hate thieir boring life, hate thier marriage, or they went off to war because of peer pressure. My Dad admitted to me years ago when I asked him why he volunteered in ’39 in join the CDN army, 1 st div. He replyed that his ford was about to be repossed by the bank, and there wasn’t any work in the 30’s. He’s dead now but I’m sure his contribution and reasons will be well respected over time.

What a Crock!
The “social capitol” , read fear of ostracism, is what gets you there in the first place. Unless you’ve got the position in society that doesn’t rebuke its members for dodging the draft for $300 was it? in the civil war, or pulling strings to get into the Air National Guard or rushing home to knock up the missus once the regs were changed to include married men, as exemplified by history’s highest profile draft-dodgers (though runners up in the war-monger category).
Throw guys down a well and if they can get out with one anothers help thats what they’ll do.

Great article. I only question the claim that “Ms. Costa and Mr. Kahn’s work reminds us that diversity has had costs as well as benefits.” Perhaps, instead, this shows that in the situations studied, the people’s lives were not diverse ENOUGH. This is only a guess, but I would imagine that people who come from diverse backgrounds, attend diverse schools, and meet people from another ethnicity/nationality/whatever from an early age would have less of this tendency to treat people unlike themselves poorly.

Overall, I think this is showing that we don’t have ENOUGH diversity, rather than too much.

“[O]ur soldiers are still risking death to protect the rest of us.” Puhleeze! The last time that was true was 1945. At the latest.

Social capital is the economics behind why soldiers fight? Perhaps in some cases, but certainly not a universal or even a major reason that could account for most of the solders fighting in all kinds of warfares.

Those cases which the author’s claim might apply could be the career soldiers in regular army in which they train together for long periods of time prior to being deployed for war. Sure, where bonds between them have been nurtured, there’s useful social capital to leverage in times of need. But just like all human relationships, hidden negative sentiments and politics could also mean, in the chaos of war, incooperative behavior. This is purely the nature of human relation, whether in army or prison camps. Social capital is not a reason why soldiers fight in this case. For if solders were interviewed during Vietnam War why they wanted to be there to fight, the answers could just well be “I didn’t want to be here!”.

In guerilla army, soldiers are formed from sporadic sources – walk-ins, trained, untrained, with various demographics – and little time to train together. Yet, they fight with entrenched determination. Their “get out of my land” mindset motivates their fighting.

In terrorist army, their soldiers are, in what has been reported, brainwashed from childhood to live in hatred and revenge. Their ideology, rightly or wrongly, motivates their fighting.

So basically and as far as my limited understanding of various natures of war goes, a mix of reasons drive the soldiers to fight, depending on the nature of war and the motivation behind the soldiers.

If social capital makes soldiers fight, what makes soldiers stop fighting and fraternize with opposing forces, as in the famous Christmas Truces of WWI? Isn’t that ‘social capital’ and human bonding, too? If so, Glaeser hasn’t explained anything. If not, then we’re looking at mysterious unknowns… and Glaeser hasn’t explained anything….