The Second World War was the hinge point for establishing American dominance. Prior to that war, the United States had focused on continental expansion, making sure its neighbours recognised its regional dominance and pre-empting the influence of European powers in the Americas. George Washington, the first American president, warned in his farewell address that the US should avoid ‘entangling alliances’. Another president, John Quincy Adams, said that America should not go abroad searching ‘for monsters to destroy’ and that its glory was in liberty, not dominion. The United States did, nevertheless, dabble in imperialism during the late nineteenth century, toppling a decaying Spanish empire to help liberate Cuba and acquiring Puerto Rico, Guam and the Philippines in the process. But, having won its own freedom in 1776 from British colonial control, there was little desire in America for it to become a colonial power itself. Even involvement in the First World War could not shake the US out of its preferred isolationist shell. The United States entered the war late, brought its forces home quickly afterwards and refused to help enforce a peace its president helped design due to the US Congress rejecting membership of the League of Nations.
The Second World War was truly global in scope and revolutionary in its impact. The United States was drawn into the conflict, again late, by German submarine warfare in the Atlantic and a surprise attack on its military facilities at Pearl Harbor by the Japanese in December 1941. When the war began in 1939 there were several powers contesting for global leadership, but the United States was not among them. The United Kingdom and France had sizeable empires. Adolf Hitler was determined to create a new German ‘Reich’ (or empire) that would last at least 1,000 years. Imperial Japan was seeking dominance in Asia and had already occupied parts of China and all of Korea. Finally, the Soviet Union had proved that a communist revolution was possible, and prospects were good that other nations would follow suit and communism would spread globally. By the war’s end Germany and Japan were devastated, defeated countries, occupied by foreign powers. Among the victors, the United Kingdom and France were spent powers. Their empires were fragmenting and their economies near-destroyed. The Soviet Union had suffered the most significant losses of all, primarily through battling a German invasion. Despite winning the war, the cost of victory for the allied powers had been high. In contrast, by 1945 the United States had shaken off the effects of the Great Depression, the global economic collapse of the 1930s, and was relatively untouched by the war. It had demonstrated its power by mobilising and equipping a military of over 16 million. As the war ended it had military forces stationed across the globe and was the world’s dominant economic power.
The United States took several lessons from the Second World War, the most important of which was that it had to be involved in managing global security in order to protect its own security. It was too big and too powerful for others not to challenge even if it had no interest in challenging them. Because international relations as a system is anarchical, with no ruler, powerful states tend to make other states feel insecure by default. Even if powerful states do not behave threateningly, there is a fear that they may do so in the future. This leads to competition and the risk of future conflict as states seek to maximise their security by attempting to increase their relative power. In the past this was typically done by acquiring territory, as described in chapter one. But in a post-war era characterised by decolonisation and the presence of nuclear weapons, security calculations were in flux. To monitor the situation, the United States chose to be involved globally, designing the international frameworks for commerce and governance at conferences it convened in Bretton Woods and San Francisco, both in America, and joining the United Nations which was headquartered in New York City. Essentially, the Americans created a new system of international relations, both economic and political, and placed themselves in the driving seat. Although the bulk of its forces were demobilised at the war’s end, the United States maintained the network of bases it had built during the war and retained a substantial military presence in both Europe and Asia. At home, it created, via the National Security Act of 1947, the governmental framework for coordinating the development and exercise of global power. In short, the United States was now permanently constituted to be a different type of actor.
Having helped destroy fascism in the Second World War, the United States set itself the task of first containing and then undermining the two remaining rival systems of global order – colonialism and communism. The test came quickly with the Soviet Union’s push to dominate Eastern Europe and its acquisition of nuclear weapons in 1949. Many American politicians feared that the Soviet Union could dominate all of Europe and Asia – an area with the industrial resources and military potential to match or even surpass the United States. When China turned communist in 1949 and other nations looked set to follow, these fears seemed to have a basis in reality. A series of confrontations and crises that we now call the Cold War became the new normal in international relations. The conflict marked a two-power struggle between the United States and the Soviet Union spanning more than forty years. IR calls this a bipolar system, as two principal actors are responsible for shaping global affairs. In the end, with the Soviet Union’s internal collapse between 1989 and 1991, there was one superpower standing – the United States. The question was, would this mean that bipolarity would give way to unipolarity (the dominance of one power) or multipolarity (many centres of power)?