The debate was beginning to change before the collapse of the Soviet Union, but has taken on even greater momentum since 1991, largely because so many Cold War-era Soviet documents became available. By the 1960s or so, Cold War historians in the West, being still, after all, in the midst of the Cold War, tended to divide into two camps: the traditional interpretation that placed the blame for the conflict on Stalinist aggression alone; and a revisionist position, influenced by the New Left, that pointed the finger more at the United States. Either way, most of these interpretations were drawn from American and Western European documents. Generally speaking, the trend after 1991 has been to complicate the old concept of the Cold War as, in one historian's words, "a Manichean conflict between the forces of monopoly capitalism and Communist totalitarianism." In the context of origins, historians today (even fairly traditionalist historians like John Lewis Gaddis) tend to emphasize contingency and to evaluate the actions of both the USSR and the United States in light of domestic economic issues, conflicts elsewhere in the world (Iran, for example) and other factors. Many diplomatic historians have come to treat the conflict as more of a international system than an actual war. Others, as alluded to above, have emphasized the importance of events outside of Europe in influencing the origins of the Cold War. So in general, Cold War historiography, including the historiography of Cold War origins has moved away from the bipolar model that many used to conceive of the conflict itself. But the most important point is that is has been the declassification of documents in all of the nations involved following the Cold War, as well as the fact that we can now look back on the conflict, that has played a major role in driving changes in the historiography.
Source: John Lewis Gaddis, The Cold War: A New History (New York: The Penguin Press, 2005)