If you think that dating the potential of American hegemony to before the Second World War is hyperbole, consider the criteria by which Spain, the Netherlands, and the United Kingdom were all retrospectively crowned hegemon; certainly the United States of the 1920s exceeded in relative power the Great Britain of the later Victorian years, when London was unable to contemplate maintaining Canada and its position in the Western Hemisphere without significant rapprochement with Washington. Had the United States bothered to maintain a significant land army or invested in its air force to a greater degree, either of which it could have afforded without a problem in either the 1920s or the 1930s, its military power coupled with its economic influence and de facto imperial hold on the Latin American countries would have certainly made it surpass the relative power position of Athens at the Periclean height. (I suspect that American influence in the Western Hemisphere peaked about 1940, which is when the FBI--the FBI!--ran U.S. intelligence operations throughout the region and external penetration of regimes was at its minimum.)
If periodizing U.S. unipolarity is such a problem, it is no less difficult than determining when the Cold War began and ended. The high school history textbook answer is 1946 to 1991, but over the past decade I have come to the radical position that everything we learn in high school is probably wrong. (Even the Pythagorean theorem.) A very informal survey of the IR literature leads me to conclude that the Cold War as understood at the time actually ended about 1971, +/- four years (in other words, within the period between Glassboro and Helsinki). The renewed pattern of hostile interactions between the invasion of Afghanistan and Reagan's second inauguration was widely seen by everyone except the editors of Human Events as a throwback or a reignition of a dormant conflict. Moreover, this Cold War ended at least three times: with the conclusion of major arms limitation talks in Europe, with the fall of the Berlin Wall and the dissolution of the Soviet Eastern European empire, and with the collapse of the U.S.S.R. itself in 1991. (For extra credit, pinpoint the dissolution of the U.S.S.R.: was it the August coup, the signing of the C.I.S. treaty, or the resignation of Mikhail Gorbachev?)
Politics ain't beanbag, and political science ain't physics. There is no shame in our having multiple definitions of the inauguration and conclusion of different eras. The different periods may be useful for different purposes. (I think it is clear as can be that 1973 marked the end of American economic hegemony and the beginning of meaningful multilateral governance of aspects of the international--read first world--economic system.) Yet the proliferation of periodizations nevertheless should prompt some epistemic humility among contemporary IR scholars and also a re-evaluation of the way we present the "stylized facts" of 20th century history to undergraduates. In particular, we should reject the high school narrative of the Cold War as a monolithic event that serves a useful analytical purpose and instead present the years between Roosevelt's death and Clinton's boxers as a series of more discrete and more analytically-defined periods. I suggest the following:
- The Cold War, 1947 to 1962. The Truman Doctrine and the Cuban Missile Crisis bookend the height of the Cold War. The Truman Doctrine symbolizes U.S. resolution to engage the Soviet Union and neatly outlines the doctrine of containment; the Cuban Missile Crisis symbolizes both the rise of Soviet power and the need of the United States to adapt to a world in which its strategic supremacy was no longer a given.
- The Soviet-American condominium, 1963-1979. The signal fact about the 1960s and the 1970s was the strategic stability of the global order, as assured destruction and concomitant strategic talks between Moscow and Washington imposed an order on bilateral relations. The "opening" to China---a far more complex event than normally portrayed---was as much a way for the United States to maintain the global order as it was for Washington to seek an advantage versus the U.S.S.R. (In particular, a Sino-Soviet war, as seemed possible in 1968 and 1969, could have had incalculable consequences for global order generally.) The Kissingerian mantra of a "structure" of global peace fits the period well, in which the drumbeat of nuclear tests had been replaced by a numbing succession of test-ban treaties and SALT talks.
- Strategic supremacy, 1979 to ?. Washington's response to the Soviet invasion of Afghanistan and the buildup of American military budgets, combined with the increasingly unsustainable Soviet economic and political structure, produced a situation in which the domestically-determined collapse of the U.S.S.R. unfolded to maximum American advantage. It was Washington, not any multipolar arrangement, that dictated the fundamentals of the post-Soviet era: a unified Germany in NATO, the deference to the use of American military power in the Gulf and later in the Balkans, and the ability of the United States to project power throughout the world.