The most basic cause of imperial collapse was the rising demand of non-Western peoples for national self-determination, racial equality, and personal dignity. This demand spread from intellectuals to ordinary people in nearly every colonial territory after the First World War. By 1939, the colonial powers were already on the defensive; the Second World War prepared the way for the eventual triumph of independence movements.

European empires had been based on an enormous power differential between the rulers and the ruled, a difference that had greatly declined by 1945. Western Europe was economically devastated and militarily weak immediately after the war. Moreover, the Japanese had driven Western imperial rulers from large parts of East Asia during the war in the Pacific. In Southeast Asia, European imperialists confronted strong anticolonial nationalist movements that re-emerged with new enthusiasm after the defeat of the Japanese.

Popular politicians, including China’s Mao Zedong, India’s Mohandas Gandhi, Egypt’s Gamal Abdel Nasser, and many others, provided determined leadership in the struggle against European imperialism. A new generation of intellectuals, such as Jomo Kenyatta of Kenya and Aimé Césaire and Frantz Fanon, both from Martinique, wrote trenchant critiques of imperial power, often rooted in Marxist ideas. Anticolonial politicians and intellectuals alike helped inspire colonized peoples to resist and overturn imperial rule.

Around the globe, the Cold War had an inescapable impact on decolonization. Liberation from colonial rule had long been a central goal for proponents of Communist world revolution. The Soviets and, after 1949, the Communist Chinese advocated rebellion in the developing world and promised to help end colonial exploitation and bring freedom and equality in a socialist state. They supported Communist independence movements with economic and military aid.

Western Europe and particularly the United States offered a competing vision of independence, based on free-market economics and, ostensibly, liberal democracy — though the United States was often willing to prop up authoritarian regimes that supported staunch anticommunism. Like the U.S.S.R., the United States extended economic aid and weaponry to decolonizing nations. The Americans promoted cautious moves toward self-determination in the context of containment, attempting to limit the influence of communism in newly liberated states.

After they had won independence, the leaders of the new nations often found themselves trapped between the superpowers, compelled to support one bloc or the other. Many new leaders followed a third way, adopting a policy of nonalignment, that is, remaining neutral in the Cold War and playing both sides for what they could get.