The 1940s (pronounced "nineteen-forties" and commonly abbreviated as "the 40s") was a decade of the Gregorian calendar that began on January 1, 1940, and ended on December 31, 1949.
Most of World War II took place in the first half of the decade, which had a profound effect on most countries and people in Europe, Asia, and elsewhere. The consequences of the war lingered well into the second half of the decade, with a war-weary Europe divided between the jostling spheres of influence of the Western world and the Soviet Union, leading to the beginning of the Cold War. To some degree internal and external tensions in the post-war era were managed by new institutions, including the United Nations, the welfare state, and the Bretton Woods system, facilitating the post–World War II economic expansion, which lasted well into the 1970s. The conditions of the post-war world encouraged decolonization and the emergence of new states and governments, with India, Pakistan, Israel, Vietnam, and others declaring independence, although rarely without bloodshed. The decade also witnessed the early beginnings of new technologies (such as computers, nuclear power, and jet propulsion), often first developed in tandem with the war effort, and later adapted and improved upon in the post-war era.