Berlin to Soviet troops, Hitler's suicide and the German unconditional surrender on 8 May 1945. Following the Potsdam Declaration by the Allies on 26 July 1945 and the refusal of Japan to surrender on its terms, the United States dropped the first atomic bombs on the Japanese cities of Hiroshima, on 6 August, and Nagasaki, on 9 August. Faced with an imminent invasion of the Japanese archipelago, the possibility of additional atomic bombings, and the Soviet entry into the war against Japan and its invasion of Manchuria, Japan announced its intention to surrender on 15 August, then signed the surrender document on 2 September 1945, cementing total victory in Asia for the Allies. World War II changed the political alignment and social structure of the globe. The United Nations (UN) was established to foster international co-operation and prevent future conflicts, and the victorious great powers—China, France, the Soviet Union, the United Kingdom, and the United States—became the permanent members of its Security Council. The Soviet Union and the United States emerged as rival superpowers, setting the stage for the nearly half-century-long Cold War. In the wake of European devastation, the influence of its great powers waned, triggering the decolonisation of Africa and Asia. Most countries whose industries had been damaged moved towards economic recovery and expansion. Political integration, especially in Europe, began as an effort to forestall future hostilities, end pre-war enmities and forge a sense of common identity. Cold War The Cold War was a period of geopolitical tension between the United States and the Soviet Union and their respective allies, the Western Bloc and the Eastern Bloc, which began following World War II. The Western Bloc was led by the United States as well as the other First World nations of the Western Bloc that were generally liberal democratic but tied to a network of the authoritarian states, most of which were their former colonies. The Eastern Bloc was led by the Soviet Union and its Communist Party, which had an influence across the Second World. The US government supported right-wing governments and uprisings across the world, while the Soviet government funded communist parties and revolutions around the world. As nearly all the colonial states achieved independence in the period 1945–1960, they became Third World battlefields in the Cold War. Early Cold War and decolonization The first phase of the Cold War began shortly after the end of