"Like the nuclear war that never came, the revival and eventual triumph of democratic capitalism was a surprising development that few people on either side of the ideological divide in 1945 would have foreseen. Circumstances during the first half of the 20th century had provided physical strength and political authority to dictatorships. Why should the second half have been different? The reasons had less to do with any fundamental shift in the means of production, as a Marxist historian might have argued, than with a striking shift in the attitude of the United States toward the international system. Despite having built the world's most powerful and diversified economy, Americans had shown remarkably little interest, prior to 1941, in how the rest of the world was governed. Repressive regimes elsewhere might be regrettable, but they could hardly harm the United States. Even involvement in World War I had failed to alter this attitude, as Wilson discovered to his embarrassment and chagrin. What did change it, immediately and irrevocably, was the Japanese attack on Pearl Harbor. That event shattered the illusion that distance ensured safety: that it did not matter who ran what on the other side of the ocean. The nation's security was now at risk, and because future aggressors with air and naval power could well follow the Japanese example, the problem was not likely to go away. There was little choice, then, but for the United States to assume global responsibilities. Those required winning the war against Japan and Germany—Hitler having declared war on the United States four days after Pearl Harbor—but they also meant planning a postwar world in which democracy and capitalism would be secure."