There were two sets of very interesting comments on my recent post on hegemony. Bill Petti questions whether US hegemony only has another few decades left in its lifespan. At the most basic level, Bill is right. I definitely overstated the case. At the same time, Bill presents far too optimistic a picture of the prospects for medium-term American primacy.

Bill argues that hegemonic decline is driven by one of four processes: “imperial overstretch, economic decline, and either purposeful retrenchment (i.e. Britain) or internal collapse (i.e. the Soviet Union).”

Let’s start with the first process: overextension The US is not, as Bill suggests, in any real danger of “imperial overstretch.” Some may find this view surprising. After all, a lot of people are talking about how the US military is badly overextended by its current commitments (particularly in Iraq) and cannot recruit sufficient new soldiers.

Our present forces are, indeed, overextended. But this isn’t a matter of actual capabilities so much as it is one of political will. American politicians, not to mention the general public, simply don’t have the appetite to make the kind of real economic and physical sacrifices required for shifting the US economy towards a real war footing. Our defense budget may dwarf that of other countries in raw terms, but it remains around 3.6% of GDP. During the Vietnam War, in contrast, US defense expenditures peaked at about 9.8% of GDP. If the US wanted to commit significantly more resources to the military, reinstate the draft, and otherwise move towards full mobilization, it could do so and shoulder a far more extensive overseas commitment than it currently does.

We should, however, be cautious about the logic of imperial “overstretch.” Hegemonic overextension clearly does happen; as Bill notes, it was a major factor in the collapse of the Soviet Union. But my own reading of a number of putative cases of hegemonic overextension is different than the conventional argument. Overstretch tends not to be an autonomous cuase of hegemonic decline, but is generally an effect of underlying problems: economic stagnation, the erosion of a hegemonic-order’s legitimacy, or counterbalancing by other states against the hegemon.1

The analytic problem here is that any declining hegemon is going to suffer, almost by definition, from overextension: the very fact of its decline will make a hegemon incapable of maintaining its foreign commitments. Thus, political overextension is often crucial to the end of hegemonies. Hegemons, or empires, tend to get into trouble when they lose the resolve to continue their commitments. The real problems come when hegemonic orders lose their legitimacy among allies and clients. This leads to escalating resistance to the hegemon, rebellions in areas the hegemon dominates, and the emergence of alliances to counter the hegemon’s influence.

The US is far from that point, but there are a number of early warning signs that suggest the general erosion of American legitimacy in the international arena may prove quite dangerous in the future.2

This all matters for John Ikenberry’s claims about the US-led hegemonic order. I think John is right that the US created a more durable order than those of the past few centuries, and that its durability is founded on more than the public goods it provides. The American hegemonic order also includes many “voice opportunities” for weaker states through international institutions. These institutions helped “bind” the US by restricting its ability to enage in unilateral action.

Indeed, these features of the post-1945 order reassured a great many states that the US would use its disproportionate power to become a kind of global predator – doing whatever it wanted to whomever it wanted. Yet the Bush administration has actively undermined key components of that order. If the US continues on this course, all bets are off. Indeed, John basically admits that much in his article for Prospect. 3

But these are, by in large, the less important reasons to think the days of US hegemony are numbers. For one, the world is clearly multipolar in an economic sense. For another, straight-line growth projections suggest declining US relative economic power for some time. Bill is right that there are a lot of unknown variables. China could implode. There are structural features of its economy that suggest it can’t sustain its current growth for that much longer. The EU could fail to get its act together, and its attempts at coordinating its defense policy have failed pretty miserably. 4

Moreover, the US still provides significant public goods, particularly in terms of global security, that create strong disincentives for most potential rivals to challenge US dominance. Yet the underlying dynamics are moving away from the US. And, as the saying goes, nothing lasts forever. The Empire on which the “Sun Never Sets” now consists, in the main, of Gibraltar, Diego Garcia, and part of Ireland.5

In the final analysis, US hegemony may last for ten years, twenty years, or even fifty or seventy years. But don’t expect it to be around much longer than that, barring a US victory in a great war or some other major changes in world politics. And even if the US continues to be the only global military great power for some time, a lot of these trends are likely to make their effects felt on the regional level long before they impact the global distribution of power.

PS: Patrick’s comments are particularly interesting, because they raise issues involved in scenario planning. I’ll try to get to them in a later post.

(This entry has been modified and edited since its initial posting)

1Most examples of hegemonic powers, such as Habsburg Spain, Imperial Rome, Victorian Britain, and Bourbon France, were also empires.
2Steve Brooks and Bill Wohlforth have been working on a paper (link is to a PDF of a draft; they have articles on the subject forthcoming in International Security and Perspectives on Politics) in which they argue that, despite lots of anti-US rhetoric, we haven’t really seen any discernible costs to the US from its unpopular policies; apparent instances of “soft balancing” (attempts to check US power through diplomatic rather than military means) are more rhetoric than substance.
3Given this, I wonder if John’s logic still works. Imagine that in 2008 a multilateralist Democrat wins the White House. That would certainly smooth things over with, for example, Europe. But given the ease with which the Bush administration alternatively shreds and shuns all manner of treaties, I am not sure it will ever be as easy again for the US to credibly commit to institutionalized restraint.
4I went to college during the era of Rising Sun, Japan as Number One, and The Japan That Can Say ‘No’. Believe me, I know better than to rely on straightforward extrapolations of current trends.
5Yeah, yeah. I know. And Scotland and Wales. And the Falklands. And Bermuda – update courtesy of Murray Gregorson, former Georgetown student, future political theorist of repute.