The Aftermath of World War II covers a period of history from roughly 1945-1957. A multipolar world was replaced by a bipolar one dominated by the two most powerful victors, the United States and Soviet Union, which became known as the superpowers.

In an effort to maintain international peace, the Allies formed the United Nations, which officially came into existence on 24 October 1945, and adopted The Universal Declaration of Human Rights in 1948, as a common standard of achievement for all member nations.

The alliance between the Western Allies and the Soviet Union had begun to deteriorate even before the war was over, and the powers each quickly established their own spheres of influence. In Europe, the continent was essentially divided between Western and Soviet spheres by the Iron Curtain which ran through and partitioned Allied occupied Germany and occupied Austria. Soviet rule was restored in the Soviet Socialist Republics annexed or enlarged in 1940, such as the Western parts of the Ukrainian SSR and Belorussian SSR, the three Baltic countries, part of eastern Finland and northeastern Romania.

Other states that the Red Army liberated at the end of the war became Soviet Satellite states, such as the People's Republic of Poland, the People's Republic of Hungary, the Czechoslovak Socialist Republic, the People's Republic of Romania, the People's Republic of Albania, and later East Germany from the Soviet zone of German occupation.

German technology was transferred to the U.S. and Soviet Union in operations Paperclip, and Osoaviakhim. Britain and the United States soon abandoned their war crimes programmes and policies of denazification in favour of realpolitik, leading to large numbers of former Nazis being allowed to emigrate to these nations and their dependencies. Secret arrangements were concluded between American military intelligence and former key figures in the anti-communist section of German military intelligence or Abwher, headed by General Reinhard Gehlen, to advise the Americans on how to go about establishing their own anti-Soviet networks in Europe.

In Asia, the United States occupied Japan and administrated Japan's former islands in the Western Pacific, while the Soviets annexed Sakhalin and the Kuril Islands; the former Japanese-governed Korea was divided and occupied between the two powers. Mounting tensions between the United States and the Soviet Union soon evolved into the formation of the American-led NATO and the Soviet-led Warsaw Pact military alliances and the start of the Cold War between them. The Republic of China occupied Taiwan.

Soon after the end of World War II, conflict flared again in many parts of the world. In China, nationalist and communist forces quickly resumed their civil war. Communist forces were eventually victorious and established the People's Republic of China on the mainland, while nationalist forces ended up retreating to Taiwan. In Greece, civil war broke out between Anglo-American supported royalist forces and communist forces, with the royalist forces victorious.

Soon after these conflicts ended, North Korea invaded South Korea, which was backed by the United Nations, while North Korea was backed by the Soviet Union and China. The war resulted in essentially a stalemate and ceasefire, after which North Korean leader Kim Il Sung created a highly centralised and brutal dictatorship, according himself unlimited power and generating a formidable cult of personality.

Following the end of the war, a rapid period of decolonization also took place within the holdings of the various European colonial powers. These primarily occurred due to shifts in ideology, the economic exhaustion from the war and increased demand by indigenous people for self-determination. For the most part, these transitions happened relatively peacefully, though notable exceptions occurred in countries such as Indochina, Madagascar, Indonesia and Algeria. In many regions, divisions, usually for ethnic or religious reasons, occurred following European withdrawal. This was seen prominently in the Mandate of Palestine, leading to the creation of Israel, and in India, resulting in the creation of the Dominion of India and the Dominion of Pakistan.

By the end of the war, the European economy had collapsed with 70% of the industrial infrastructure destroyed. The property damage in the Soviet Union consisted of complete or partial destruction of 1,710 cities and towns, 70,000 villages/hamlets, and 31,850 industrial establishments. Economic recovery following the war was varied in differing parts of the world, though in general it was quite positive. In Europe, West Germany recovered quickly and doubled production from its pre-war levels by the 1950s. Italy came out of the war in poor economic condition, but by 1950s, the Italian economy was marked by stability and high growth. The United Kingdom was in a state of economic ruin after the war, and continued to experience relative economic decline for decades to follow.

France rebounded quickly, and enjoyed rapid economic growth and modernisation. The Soviet Union also experienced a rapid increase in production in the immediate post-war era. In Asia, Japan experienced incredibly rapid economic growth, becoming one of the most powerful economies in the world by the 1980s.

China, following the conclusion of its civil war, was essentially a bankrupt nation. By 1953, economic restoration seemed fairly successful as production had resumed pre-war levels. This growth rate mostly persisted, though it was briefly interrupted by the disastrous Great Leap Forward economic experiment. At the end of the war, the United States produced roughly half of the world's industrial output; by the early 1970s though, this dominance had lessened significantly.

Aftermath of World War II: The Allies established occupation administrations in Austria and Germany. The former would eventually become fully independent and neutral state, non-aligned with any political bloc. The latter was divided onto western and eastern occupation zones controlled by the Western Allies and the USSR, accordingly. A wholesale denazification program was started in Germany immediately after the war ended, leading to prosecution of major Nazi war criminals and removal of many ex-Nazi from power, although this policy would be replaced soon by the policy of broad amnesty and re-integration of ex-Nazi into new West German society. Germany lost part of its eastern territories: Silesia, Neumark and most of Pomerania were transferred to Poland, whereas East Prussia was divided between Poland and the USSR, followed by the transfer of the German population from these provinces, as well as from Czechoslovakia, to Germany. The USSR also annexed part of Polish territory east from the Kurzon line, Eastern Romania, part of eastern Finland and three Baltic states.

In an effort to maintain international peace, the Allies formed the United Nations, which officially came into existence on 24 October 1945, and adopted The Universal Declaration of Human Rights in 1948, as a common standard of achievement for all member nations. The alliance between the Western Allies and the Soviet Union had begun to deteriorate even before the war was over, Germany had been de facto divided, and two independent states, Federal Republic of Germany and German Democratic Republic were created within the borders of Allied and Soviet occupation zones, accordingly. The rest of Europe was also divided onto Western and Soviet spheres of influence. Most eastern and central European countries fell into the Soviet sphere of influence, which led to establishment of Communist led regimes there, with full or partial support of the Soviet occupation authorities. As a result, Poland, Hungary, Czechoslovakia, Romania, Albania, and East Germany became Soviet Satellite states. By contrast, Communist Yugoslavia conducted fully independent policy which had eventually lead to significant tensions with the USSR.

Post-war division of the world was formalised by two international military alliances, the United States-led NATO and the Soviet-led Warsaw Pact; the long period of political tensions and military competition between them, the Cold War, would be accompanied by unprecedented arm race and proxy wars.

In Asia, the United States occupied Japan and administrated Japan's former islands in the Western Pacific, while the Soviets annexed Sakhalin and the Kuril Islands.^[241] Korea, formerly under Japanese rule, was divided and occupied by the US in the South and the Soviet Union in the North between 1945 and 1948. Separate republics emerged on both sides of the 38th parallel in 1948, each claiming to be the legitimate Korean sovereign, which led ultimately to the Korean War. In China, nationalist and communist forces resumed the civil war in June 1946. Communist forces were eventually victorious and established the People's Republic of China on the mainland, while nationalist forces ended up retreating to Taiwan in late 1949. While the European colonial powers attempted to retain some or all of their colonial empires, their losses of prestige and resources during the war rendered this unsuccessful, leading to rapid decolonisation.

The global economy suffered heavily from the war, although different WWII participants were affected differently. The US emerged much richer than any other nation involved in World War II; by 1950 its gross domestic product per person was much higher than that of any of the other major powers and it dominated the world economy. However, economic recovery following the war was rather fast, though it varied in differing parts of the world. In most of West Europe, recovery was fast, partially due to massive American economic aid: heavily devastated West Germany recovered quickly, and doubled production from its pre-war levels by the 1950s; the Italian economy was also rapidly growing; France rebounded quickly, and enjoyed rapid economic growth and modernisation. By contrast, the United Kingdom was in a state of economic ruin after the war, and continued to experience relative economic decline for decades to follow. The Soviet Union, despite enormous human and material losses, also experienced a rapid increase in production in the immediate post-war era. Japan experienced incredibly rapid economic growth, becoming one of the most powerful economies in the world by the 1980s. China returned to its pre-war industrial production by 1952.