Answer by Matthew Spencer:
The Second World War was a decisive factor in decolonization worldwide. Nazi Germany waged what in many respects could be called a neocolonial war in Eastern Europe. Japan’s policy of creating, through force, what it called The Greater East Asia Co-prosperity Sphere was an analogous development in the Pacific. The catastrophic consequences of both efforts did much to discredit the idea of expansion and empire building as a central plank of government policy.
The war did much to discredit official racism as well. The Germans and Japanese were certainly not alone in thinking that different peoples in different parts of the world were inherently inferior or superior. But after 1945, arguments favoring eugenics or the so-called duty to civilize “savage” peoples could not withstand the weight of those associations.
On a more pragmatic dimension, the Second World War did serious damage to the major colonial powers of the time: France, Belgium, Great Britain and The Netherlands. Anticolonial political leaders such as Ho Chi Minh saw their chance to achieve independence within this power vacuum.
The surviving superpowers, the USA, the Soviet Union, and Communist China, could in many ways be seen as imperialistic and neocolonial, but all of those nations favored the exercise of political, military and economic power by proxy. There were areas that were annexed. For example, the Soviet Union took parts of East Prussia, and China invaded and settled Tibet, but these are exceptions rather than the rule.
The end of the Second World War marked a new phase in international politics, one in which nations do not officially rule over vast foreign territories but instead exercise power through military interventions, economic investment or sanctions, cultural change through mass media and numerous other channels of influence.
Whether or not this is truly imperialism is a discussion unto itself, but no one can deny the massive level of power that the US, Russia, and China exert on an international level. But what also can’t be denied is that the forms this power takes are profoundly different compared to imperial politics a hundred years ago.