This post is an overview of the 2014 book by Stanford classicist Ian Morris, War! What Is It Good For? In it he makes the counter-intuitive argument that over time some forms of war have been socially productive. In contrast with the message of 1970s song by the same name, war may in fact be good for something.
The central story is this. Some wars lead to the incorporation of large numbers of people under a single imperial state. In the short run, this is devastatingly destructive; but in the long run it can be quite beneficial. Under such regimes (e.g., the early Roman and Chinese empires and the more recent British and American empires), the state imposes a new order that sharply reduces rates of violent death and fosters economic development. The result is an environment that allows the population live longer and grow wealthier, not just in the imperial heartland but also in the newly colonized territories. 
So how does this work? He starts with a key distinction made by Mancur Olson. All states are a form of banditry, Olson says, since they extract revenue by force. Some are roving bandits, who sweep into town, sack the place, and then move on. But others are stationary bandits, who are stuck in place. In this situation, the state needs to develop a way to gain the greatest revenue from its territory over the long haul, which means establishing order and promoting economic development. It has an incentive to foster the safety and productivity of its population.
Rulers steal from their people too, Olson recognized, but the big difference between Leviathan and the rape-and-pillage kind of bandit is that rulers are stationary bandits. Instead of stealing everything and hightailing it, they stick around. Not only is it in their interest to avoid the mistake of squeezing every last drop from the community; it is also in their interest to do whatever they can to promote their subjects’ prosperity so there will be more for the rulers to take later.
This argument is an extension of the one that Thomas Hobbes made in Leviathan:
Whatsoever therefore is consequent to a time or war where every man is enemy to every man, the same is consequent to the time wherein men live without other security than what their own strength and their own invention shall furnish them withal. In such condition there is no place for industry, because the fruit thereof is uncertain, and consequently no culture of the earth, no navigation nor use of the commodities that may be imported by sea, no commodious building, no instruments of moving and removing such things as require much force, no knowledge of the face of the earth; no account of time, no arts, no letters, no society, and, which is worst of all, continual fear and danger of violent death, and the life of man solitary, poor, nasty, brutish, and short.
(Wow, that boy could write.)
Morris says that stationary bandit states first arose with the emergence of agriculture, when tribes found that staying in place and tending their crops could support a larger population than roving across the landscape hunting and gathering. This leads to what he calls caging. People can’t easily move and the state has an incentive to protect them from marauders so it can harvest the surplus from this population for its own benefit.
Over time, these states have reduced violence to an extraordinary extent, reining in “the continual fear and danger of violent death.”
Averaged across the planet, violence killed about 1 person in every 4,375 in 2012, implying that just 0.7 percent of the people alive today will die violently, as against 1–2 percent of the people who lived in the twentieth century, 2–5 percent in the ancient empires, 5–10 percent in Eurasia in the age of steppe migrations, and a terrifying 10–20 percent in the Stone Age.
In the process, states found that they prospered most when they relaxed direct control of the economy and allowed markets to develop according to their own dynamic. This created a paradoxical relationship between state and economy.
Markets could not work well unless governments got out of them, but markets could not work at all unless governments got into them, using force to pacify the world and keep the Beast at bay. Violence and commerce were two sides of the same coin, because the invisible hand needed an invisible fist to smooth the way before it could work its magic.
Empires, of course, don’t last forever. At a certain point, hegemony yields to outside threats. One chronic source of threat in Eurasian history was the roving bandit states of the Steppes that did in Rome and constantly harried China. Another threat is the rise of a new hegemon. The British global empire of the 18th and 19th century fostered the emergence of the United States, which became the empire of the late 20th and early 21st century, and this in turn fostered the development of China.
And there can be long periods of time between empires, when wars are largely unproductive. After the fall of Rome, Europe experienced nearly a millennium of unproductive wars, as small states competed for dominance without anyone ever actually attaining it, a condition he calls “feudal anarchy.” The result of a sharp increase in violence and and sharp decline in standard of living. It wasn’t until the 16th century that Europe regained the per capita income enjoyed by Romans.
It seems to me, in fact, that “feudal anarchy” is an excellent description not just of western Europe between about 900 and 1400 but also of most of Eurasia’s lucky latitudes in the same period. From England to Japan, societies staggered toward feudal anarchy as their Leviathans dismembered themselves.
But 1400 saw the beginning of the 500-year war in which Europe strove mightily to dominate the world, finally producing the imperium of the British and then the Americans.
Morris’s conclusion from this extensive analysis is disturbing but also compelling:
The answer to the question in this book’s title is both paradoxical and horrible. War has been good for making humanity safer and richer, but it has done so through mass murder. But because war has been good for something, we must recognize that all this misery and death was not in vain. Given a choice of how to get from the poor, violent Stone Age to … peace and prosperity…, few of us, I am sure, would want war to be the way, but evolution—which is what human history is—is not driven by what we want. In the end, the only thing that matters is the grim logic of the game of death.
…while war is the worst imaginable way to create larger, more peaceful societies, it is pretty much the only way humans have found.
