No country in modern history has possessed as much global military power as the US. Yet some analysts now argue that the US is following in the footsteps of the UK, the last global hegemon to decline. This historical analogy, though increasingly popular, is misleading.

Britain was never as dominant as the US is today. To be sure, it maintained a navy equal in size to the next two fleets combined, and its empire, on which the sun never set, ruled over a quarter of humankind. But there were major differences in the relative power resources of imperial Britain and contemporary America. By the outbreak of World War I, Britain ranked only fourth among the great powers in terms of military personnel, fourth in terms of GDP, and third in military spending.

The British Empire was ruled in large part through reliance on local troops. Of the 8.6 million British forces in WWI, nearly a third came from the overseas empire. That made it increasingly difficult for the government in London to declare war on behalf of the empire when nationalist sentiments began to intensify.

By World War II, protecting the empire had become more of a burden than an asset. The fact that the UK was situated so close to powers like Germany and Russia made matters even more challenging.

Power hungry
For all the loose talk of an ‘American empire’, the fact is that the US does not have colonies that it must administer, and thus has more freedom to manoeuvre than the UK did. And, surrounded by unthreatening countries and two oceans, it finds it far easier to protect itself.

That brings us to another problem with the global hegemon analogy: the confusion over what hegemony actually means. Some observers conflate the concept with imperialism; but the US is clear evidence that a hegemon does not have to have a formal empire. Others define hegemony as the ability to set the rules of the international system; but precisely how much influence over this process a hegemon must have, relative to other powers, remains unclear.

Still others consider hegemony to be synonymous with control of the most power resources. But, by this definition, 19th century Britain – which at the height of its power in 1870 ranked third (behind the US and Russia) in GDP and third (behind Russia and France) in military expenditures – could not be considered hegemonic, despite its naval dominance. Similarly, those who speak of American hegemony after 1945 fail to note that the Soviet Union balanced US military power for more than four decades. Though the US had disproportionate economic clout, its room for political and military manoeuvre was constrained by Soviet power.

Fact and fiction
Some analysts describe the post-1945 period as a US-led hierarchical order with liberal characteristics, in which the US provided public goods while operating within a loose system of multilateral rules and institutions that gave weaker states a say. They point out that it may be rational for many countries to preserve this institutional framework, even if American power resources decline. In this sense, the US-led international order could outlive America’s primacy in power resources, though many others argue that the emergence of new powers portends this order’s demise.

But, when it comes to the era of supposed US hegemony, there has always been a lot of fiction mixed in with the facts. It was less a global order than a group of like-minded countries, largely in the Americas and Western Europe, which comprised less than half of the world. And its effects on non-members – including significant powers like China, India, Indonesia, and the Soviet bloc – were not always benign. Given this, the US position in the world could more accurately be called a ‘half-hegemony.’

Of course, America did maintain economic dominance after 1945: the devastation of WWII in so many countries meant that the US produced nearly half of global GDP. That position lasted until 1970, when the US share of global GDP fell to its pre-war level of one-quarter. But, from a political or military standpoint, the world was bipolar, with the Soviet Union balancing America’s power. Indeed, during this period, the US often could not defend its interests: the Soviet Union acquired nuclear weapons; communist takeovers occurred in China, Cuba, and half of Vietnam; the Korean War ended in a stalemate; and revolts in Hungary and Czechoslovakia were repressed.

A new era
Against this background, primacy seems like a more accurate description of a country’s disproportionate (and measurable) share of all three kinds of power resources: military, economic, and soft. The question now is whether the era of US primacy is coming to an end.

Given the unpredictability of global developments, it is, of course, impossible to answer this question definitively. The rise of transnational forces and non-state actors, not to mention emerging powers like China, suggests that there are big changes on the horizon. But there is still reason to believe that, at least in the first half of this century, the US will retain its primacy in power resources and continue to play the central role in the global balance of power.

In short, while the era of US primacy is not over, it is set to change in important ways. Whether or not these changes will bolster global security and prosperity remains to be seen.