World War II, lasting from 1939 to 1945, was a global conflict involving over 30 countries. It resulted in an estimated 70-85 million fatalities, making it the deadliest war in history. Major powers included the Allies (USA, USSR, UK) and Axis (Germany, Japan, Italy). Key events include the Holocaust, D-Day, and the atomic bombings of Hiroshima and Nagasaki.
