World War II began on September 1, 1939 when Germany invaded Poland. On September 17, the Soviet Union invaded Poland from the east, dividing the country between Germany and the USSR. The Soviets captured 250,000 Polish prisoners of war, most of whom were denied legal status. Between 1939-1941, the Soviets arrested and imprisoned 500,000 Poles, with at least 150,000 dying. The Soviets also deported over 1.2 million Poles in four waves between 1940-1941, sending them by cramped train to remote parts of the USSR, where many died during the difficult journey or from harsh treatment and living conditions.