"What never happened, despite universal fears that it might, was a full-scale war involving the United States, the Soviet Union, and their respective allies. The leaders of these countries were probably no less belligerent than those who had resorted to war in the past, but their bellicosity lacked optimism: for the first time in history no one could be sure of winning, or even surviving, a great war. Like the barbed wire along the Hungarian border, war itself-—at least major wars fought between major states—had become a health hazard, and therefore an anachronism. The historical currents that produced this outcome are not difficult to discern. They included memories of casualties and costs in World War II, but these alone would not have ruled out future wars: comparable memories of World War I had failed to do so. J. Robert Oppenheimer hinted at a better explanation when he predicted in 1946 that "if there is another major war, atomic weapons will be used." The man who ran the program that built the bomb had the logic right, but the Cold War inverted it: what happened instead was that because nuclear weapons could be used in any new great power war, no such war took place. By the mid-1950s these lethal devices, together with the means of delivering them almost instantly anywhere, had placed all states at risk. As a consequence, one of the principal reasons for engaging in war in the past—the protection of one's own territory—no longer made sense. At the same time competition for territory, another traditional cause of war, was becoming less profitable than it once had been. What good did it do, in an age of total vulnerability, to acquire spheres of influence, fortified defense lines, and strategic choke-points? It says a lot about the diminishing value of such assets that the Soviet Union, even before it broke up, peacefully relinquished so many of them."