Joseph Stalin assumed power over the Soviet Union in 1933 as Lenin's successor. He had a shrewd concept of politics and his number one goal was to make the Soviet Union into a major player on the world stage. To do this, Stalin had to start building up the Soviet's economy and in modernizing the military. He had tanks and guns made over food, housing, and consumer goods. This was his way of changing the Soviet Unions from a preindustrial society to a modern country, capable of overthrowing other nations. In acheiving his goals, Stalin had no concern for human life if it stood in the way of progress. Adolf Hitler was his only rival when it came to mass murder. Historians believe that as many as twelve million people died from standing in the war of Stalin's ambitions. Millions died from starvation and overworking even though they had no political beliefs whatsoever. In 1939 at around the beginning of World War II, Stalin signed a nonaggression pact with the Germans which stated that the Nazi's would not attck the Soviets and the Soviets would do the same. As a part of this deal, Poland was invaded and split up between Germany and the Soviet Union. Stalin although not liking this deal, saw that Hitler would invade the Soviet Union sometime in the future and this pact allowed him to prepare for it. Eight days after the pact was signed, Germany invaded Poland and World War II began. Years later, Pearl Harbor was hit by Japan and the United States entered the war. President Roosevelt teamed up with Winston Churchill of Great Britain and Stalin to form the "Big Three", a group commited to destroying Hitler and the expanding Nazi empire. One reason the United States got along so well with the Soviet Union was because Roosevelt had started an effort in changing America's view of the Soviet Union. The three leaders held conferences together of which the most important one was held at Yalta. There they discussed the Soviets help in fighting the Japanese. But as the Axis powers were being defeated, the bond between the Soviet Union and the other two nations in the "Big Three" began to fall apart. Roosevelt had died and Harry Truman had taken over the Presidency. Once the War was over, Truman demanded free election in the East European countries that were taken over during the war and now set free. Stalin opposed this idea stating, "A freely elected government in any of these East European countries would be anti-Soviet and that we cannot allow." One of Stalin's post-war plans was to repress the millions of Soviet citizens who were living outside of the soviet border when the war ended. Some were captured by the Nazi's while other were just living abroad. Stalin demanded that these "traitors" were sent back to the Soviet Union and they were shipped off to forced-labor camps, no better than the camps that the Nazi's had in WWII. More than 50 percent who went to these camps never came out. In 1953, Stalin died after twenty-five years of power. He had brought the government of Lenin and his revolutionary Bolsheviks back to the dictatorship. After his death, reformers led by Nikita Khrushchev argued for major innovations. This started the "de-stalinization" period of Soviet history.