It’s the million-dollar question of international relations scholarship: Why are some states stronger than others? The prevailing theory says that military power is the direct result of material resources—size of the defense budget, number of soldiers, or stockpiles of materiel. But in empirical studies, material resources are no better than a coin toss at predicting victory in battle. Other theories have sprung up to compensate: Perhaps “nonmaterial” factors such as democratic institutions, Western culture, or good civil-military relations are the keys to military power. Try again, says Columbia University political scientist Michael Beckley: In 381 battles fought since 1900, the single best measure for predicting which side emerged victorious was a country’s income per capita.
Could it really be so simple? Beckley says that the problem with the material resources theory is that it doesn’t account for economic development and its bedfellows—technology, infrastructure, and human capital. An undeveloped nation can pour all the money it wants into its military, but without the right tools and educated leaders, it’s no match for a rich country’s force. (America’s loss in Vietnam is the most obvious counterexample; Beckley suggests it is the exception that proves the rule.)
Democracy, Western culture, and other intangibles serve as good proxies for economic development, but Beckley finds that when he holds gross domestic product per capita constant, those other measures fail to explain variations in military power. Democracy actually seems to substantially weaken nations on the whole. It just so happens that democracy has gone hand in hand with economic development, which has masked the negative effects of democracy on military power. That relationship may not last forever, and in the next century, economic (and therefore military) powerhouses may rise that are anything but democratic.
Beckley says that having a tool for accurately predicting a victor could help forestall “foolish” incursions. “Wars,” he writes, “are fought over a variety of issues, but most share a fundamental cause: false optimism.” When both states think they can win, they’ll take up arms. Perhaps if they have a hard measure of their chances of success, weaker countries won’t be so quick to sound the trumpets.