Last week, a conference on “Aging Asia: Demographic Decline in Asia and the Future of Regional Security” convened in the historic Mahan Reading Room at the Naval War College. As the conference title suggests, a group of demographers, historians, and security specialists pondered the interplay among aging populations, shrinking manpower, foreign policy, and military affairs. I gave a historical and theoretical overview derived from my chapter in a recent book on demographics and great power politics. The question I set for myself: does dwindling manpower make states gun-shy? My answer: it depends.
Most participants seemed to assume aging nations will avoid perilous foreign ventures, especially those involving the use of military force. This stands to reason, doesn’t it? If our sons (and daughters, in countries with integrated armed forces) are few in number, each one of them is increasingly precious – not only for sentimental reasons but because they represent the next generation of entrepreneurs, political leaders, and taxpayers. In economic terms, human capital is increasingly “lumpy” in aging societies. Why expose that capital to the vagaries of battle? Better to preserve the sinews of national strength.
Caution, conservatism, and risk aversion should be the watchwords for how aging societies conduct martial affairs. There seems to be ample theoretical backing for the assumption that demographic decline begets risk aversion. Look no further than the writings of strategic theorist Carl von Clausewitz, who maintains that the value of the political object determines the magnitude and duration of the effort a state puts into attaining that object. Or, in simpler words, how much importance political leaders assign a goal determines how much stuff and how many lives they are prepared to apply to the effort, and for how long. This is straightforward cost/benefit analysis.
But magnitude is a relative term. If a nation has less and less manpower to tap for military enterprises, the apparent magnitude of each effort grows. To keep Clausewitz’s calculus in balance, an endeavor must be of surpassing importance to justify incurring significant casualties. The range of potential military engagements narrows by his remorseless logic. Trouble is, it doesn’t always work out that way. It’s probably true that a bleak demographic outlook prods leaders toward caution, but the size of the manpower pool doesn’t trump the myriad other factors that human competition engages.
One of history’s greatest strategists, former New York Yankees manager Yogi Berra, reportedly declared that “It’s tough to make predictions, especially about the future.” And if he didn’t say it, he should have. We can’t draw a straight line from demographics – or any other single factor – to a society’s strategic behavior. As it turns out, Clausewitz agrees with the great Yogi. Competitive interactions, he says, take place shrouded in “fog,” or in a “twilight,” because so many variables are in play at any time, because of the strong passions warlike enterprises rouse, and because the other antagonist gets a say in the outcome.
As it happens, the Peloponnesian War that convulsed the Greek world two millennia ago (431-404 B.C.) pitted combatants with severe demographic travails against each other. Sparta was a military oligarchy that fielded Greece’s most fearsome army. The Spartans had adopted bizarre demographic practices. For instance, they discarded infants deemed imperfect shortly after birth. They also deliberately undercut their military manpower. The army depended on an impenetrable phalanx, an interlocking formation of infantrymen. Hosts crashed into each other on the battlefield, and the strongest and most disciplined usually prevailed.
“Spartiates,” the elite of the elite, anchored the front ranks of the phalanx. These were buff guys who spent all day, every day, working out at Gold’s Gym. Spartan society was designed to afford Spartiates the leisure to continuously hone their battle prowess. Perversely, though, the city’s leadership seemed to go out of its way to keep down their numbers. Only the first-born son of a Spartiate was eligible to become a Spartiate, for example. Their brothers were out of luck, whatever their gifts for warfare. City fathers assumed this military caste would replenish itself on a one-to-one basis – a suspect assumption considering the hazards and the omnipresence of warfare in antiquity. In short, the Spartans faced a demographic crisis of their own making even before the onset of the Peloponnesian War.
Fate exacerbated matters in 465-464 B.C., when an earthquake demolished the city – and collapsed the roof of Gold’s Gym on the rising generation of Spartiates. Some two-thirds of them perished. Imagine the effect on Spartan decision-making when natural disaster suddenly reduced the 300 Battle of Thermopylae fame to the “100.” The Spartans undertook some limited adjustments to their social system as the fifth century wore on, liberalizing requirements for military service. Still, lesser soldiers increasingly comprised the front ranks of the phalanx. Remedial measures weren’t nearly enough to keep pace with battle losses. Quality suffered.
Spartiate numbers trended inexorably downward. The Spartans sued for peace at one point in the Peloponnesian War because a small contingent of Spartiates – fewer than 200 – had been captured in battle. That’s a measure of the demographic stress under which the city was waging war. A mere 700 of these elite warriors took the field against Thebes at the Battle of Leuktra in 371 B.C. – the defeat that sealed Sparta’s downfall. In a real sense, Sparta was a victim of self-defeating demographic policies, despite the famous caution and conservatism with which leaders comported themselves – and for which more venturesome allies like Corinth castigated them.
The Spartans’ foemen, the Athenians, were diametrically opposed to them in most respects. A freewheeling, democratic, maritime empire, Athens gave free vent to citizens’ energy and innovation. Its navy was unmatched in the Mediterranean world. Yet Athens suffered a demographic trauma of its own. Pericles, the city’s “first citizen,” convinced the Athenian assembly to bring the entire population of the surrounding countryside within the city walls. That let the Athenian army avoid a land battle it stood little chance of winning, and it freed the Athenian navy to run wild around Greek coasts.
Thus confined, though, the Athenian populace was neatly packaged for disease and death. A plague ravaged the city for several years in the early stages of the war, costing it an estimated 25 percent to 30 percent of the populace. That’s on the order of the Thirty Years’ War that depopulated Germany in the seventeenth century. Far from instilling prudence, however, this demographic shock released all manner of schemes for conquest and glory. With few checks on rash policies – Athenian democracy essentially entrusted decision-making to whichever citizens showed up for the assembly on a given day – the city ran amok. Pericles fell to the pestilence, removing the chief stabilizing influence.
Ultimately adventurers like Alcibiades – think Charlie Sheen with military acumen – cajoled the assembly into a disastrous invasion of Sicily. The city also doubled down on failure, dispatching reinforcements when the going got tough against Syracuse, the island’s dominant city-state. Athens ended up losing its entire expeditionary fleet – one of the pillars of Athenian power – and the entire army that fleet had transported. Only then did the Athenians start playing defense, and showing signs of risk aversion. Neither demographics nor cost/benefit logic compelled Athenians to exercise self-restraint. They did so when destruction stared them in the face.
Athens and Sparta, then, supply two different models for how states respond to demographic stress. China came up repeatedly during the Newport conference, both because of its intrinsic importance and because – like Sparta – it has distorted the makeup of the population through conscious policy. How the results of the one-child policy will affect Beijing’s strategic behavior in the coming decades remains to be seen. Will it act more like Sparta as the populace ages, conserving increasingly scarce human capital? Will it act more like Athens, and cast off restraint? Or could it embrace the Athenian model in the immediate future, locking in its status as Asia’s central power before population numbers crest and start falling – then become more Spartan to conserve its gains?
Such questions are worth asking not just for China but for India, the United States, Europe, and any other consequential actor on the world stage. Demographics specialists are right. Population figures are an important element in how nations conduct themselves. But let’s not surrender to the notion that demographics is destiny.
James Holmes is an associate professor of strategy at the US Naval War College and a contributor to Population Decline and the Remaking of Great Power Politics(2011). The views voiced here are his alone.