World War II

World War II (1939-1945) was the deadliest and most destructive conflict in human history. An estimated 70-85 million people died — about 3% of the world's 1940 population — including the systematic murder of 6 million Jews and millions of others in the Holocaust. Beginning with Germany's invasion of Poland on September 1, 1939, the war ultimately involved virtually every nation on Earth in two opposing military alliances: the Allies (primarily the UK, USA, Soviet Union, France, China) and the Axis (Germany, Japan, Italy). The war featured unprecedented industrial-scale destruction, civilian targeting, genocide, and technological warfare — including jet aircraft, missiles, radar, and ultimately nuclear weapons. The atomic bombings of Hiroshima (August 6) and Nagasaki (August 9, 1945) killed 110,000-210,000 people and led to Japan's surrender. WWII's aftermath reshaped the world: it created the United Nations, established the United States and Soviet Union as superpowers, began the Cold War, accelerated decolonization, and established international human rights norms and the state of Israel.