World War II, the largest and deadliest conflict in human history, involved more than 50 nations and was fought on land, sea and air in nearly every part of the world. Also known as the Second World War, it was caused in part by the economic crisis of the Great Depression and by political tensions left unresolved following the end of World War I.
The war began when Nazi Germany invaded Poland in 1939 and raged across the globe until 1945, when Japan surrendered to the United States after atomic bombs were dropped on Hiroshima and Nagasaki. By the end of World War II, an estimated 60 to 80 million people had died, including up to 55 million civilians, and numerous cities in Europe and Asia were reduced to rubble.
Among the people killed were 6 million Jews murdered in Nazi concentration camps as part of Hitler’s diabolical “Final Solution,” now known as the Holocaust. The legacy of the war included the creation of the United Nations as a peacekeeping force and geopolitical rivalries that resulted in the Cold War.