World War II was a war fought in two different theaters: the Pacific Theater, fought against Japan, and the European Theater, fought against Germany and Italy. Both were fought simultaneously.
In the European Theater, the German position was collapsing on two fronts. After the defeat at Stalingrad, German forces were gradually pushed out of Russia. Meanwhile, the Allies sought to open up a second front, first invading Italy (and forcing them out of the war) and then by landing on Normandy Beach. The Allies advanced from the west through France and Russia swept through Eastern Europe. Germany surrendered on May 8, 1945, and was then divided into occupied zones, to eventually be consolidated into two separate countries, with West Germany and Soviet controlled East Germany. At the same time, the Soviet Union retained hegemony throughout Eastern Europe, resulting in the so-called Iron Curtain and the Communist Bloc. From this perspective, the resolution of World War II, aside from ending the Second World War, also set the stage for the Cold War that would continue to dominate politics through much of the twentieth century.
Meanwhile, in the Pacific Theater, the Allies closed in on Japan by way of island-hopping across the Pacific. Ultimately, the United States forced an unconditional surrender by dropping Atomic Bombs on Hiroshima and Nagasaki, thereby ending the war. In the post-War period, Japan, under US occupation, was rebuilt and given a new Constitution. At the same time, the Civil War in China between the Communists and Nationalists resumed, resulting in a Communist Victory under Mao Zedong. Additionally, Korea was divided into Soviet and American occupation zones, which would shape the division of the country into North and South Korea.