Abstract
American foreign policy analysts have generally viewed World War II as the most important of the six wars the country fought in the twentieth century. By entering this war, so the argument goes, the United States prevented the gravest geopolitical threat to its security-German and Japanese hegemonies in Eurasia-from materializing. Careful reexamination of the best case for U.S. entry into World War II, made by Nicholas Spykman in 1942, demonstrates that the traditional view is misplaced: the United States could have remained secure over the long term had it not entered the war and had it allowed Germany and Japan to win. Its standard of living and its way of life, however, would most likely have suffered. Avoidance of those two outcomes was the real reason to have entered the war. The implications of this analysis for balance of power theory and current American grand strategy are spelled out.