World War II
World War II (1939-1945) was the deadliest conflict in human history, fought between the Allied Powers and the Axis Powers across Europe, Asia, Africa, and the Pacific.
No conflict in human history has matched its scale or death toll, and few have reshaped the global order as decisively, setting the terms for the geopolitics of the following eighty years.
The Outbreak of War
The war began in Europe on September 1, 1939, when Nazi Germany, under Adolf Hitler, invaded Poland, prompting Britain and France to declare war two days later. Germany's rapid conquest of much of Western Europe followed over the next year, employing new fast-moving tactics that came to be known as blitzkrieg, or "lightning war."
A Truly Global Conflict
The war expanded dramatically after Japan's surprise attack on the U.S. naval base at Pearl Harbor on December 7, 1941, which brought the United States fully into the conflict on both the European and Pacific fronts. Fighting eventually spanned nearly every inhabited continent, involving more than 30 countries and over 100 million military personnel.
Unprecedented Atrocities
The war saw devastation on a scale never before witnessed, including the Holocaust, in which Nazi Germany systematically murdered six million Jews and millions of others including Roma people, disabled individuals, and political prisoners, in an organized campaign of genocide across occupied Europe.
The Atomic Age Begins
In August 1945, the United States dropped atomic bombs on the Japanese cities of Hiroshima and Nagasaki, marking the first and only wartime use of nuclear weapons and hastening Japan's surrender, which came on September 2, 1945.
Reshaping the World
The war's end reshaped the global political order, leading to the founding of the United Nations to help prevent future conflicts, the beginning of the Cold War rivalry between the United States and Soviet Union, and the eventual decolonization of much of Africa and Asia over subsequent decades.
