The major counterinsurgency wars of decolonization of the mid twentieth century were fought by the four European imperial nations, Britain, France, the Netherlands, and Portugal. They were asymmetric campaigns, which involved regular regiments in action against a wide variety of Asian and African non-state-actor groups. During the interwar period, British experiences in Ireland, Palestine, and India had highlighted the need for counterinsurgency training and tactics, especially for riot control and cordon-and-search operations. French experiences in Morocco and Syria had suggested the same lessons.

World War II aroused further anticolonial nationalism, while in Britain doubts emerged over the legitimacy of colonial rule. The Atlantic Charter, the formation of the United Nations, and the anticolonial views of US President Roosevelt brought colonialism to the forefront of international attention. The humiliating military reverses suffered during the war by Britain, France, and the Netherlands negated much of the residual respect for the strength of the colonial powers. Furthermore, the use by Britain and France of troops recruited from colonial peoples opened new mental horizons. Indian soldiers who fought fascism in Africa or Italy saw themselves fighting for their own freedom after the war. African soldiers who fought for the British in Burma or the French in Italy or France developed similar views; and a number of them figured later as insurgent leaders. Independence for India and Pakistan in 1947 and, a little later, for Ceylon, Burma, and almost all the Dutch East Indies provided further encouragement for nationalists in the remaining colonial territories.