The World War Era
Learn about the World War Era — the catastrophic period of global conflict from 1914 to 1945 that killed over 100 million people and reshaped civilization.
The World War Era (1914–1945) encompasses the two most destructive conflicts in human history and the troubled peace between them — a period that killed over 100 million people, destroyed empires, created new nations, produced the atomic bomb, and fundamentally reshaped the global order.
Some historians view the era as a single 'Thirty Years' War' of the 20th century, in which World War I's unresolved tensions produced World War II. The first war destroyed the old European order of empires and aristocracies. The interwar period failed to build a stable replacement. The second war completed the destruction, leaving Europe in ruins and shifting global power to the United States and the Soviet Union.
The era's lessons — about the consequences of unchecked nationalism, the fragility of peace, the horrors of total war and genocide, and the need for international cooperation — shaped the postwar institutions that still govern international relations: the United Nations, NATO, the European Union, and the rules-based international order.
Lessons covering this topic
Browse all lessons →Causes of World War I
Alliances, arms races, and the assassination that started it all.
The War in the Trenches
Technology, total war, and the death of innocence.
The Road to World War II
Appeasement, expansion, and the failure of peace.
The Global Conflict
From Blitzkrieg to the Pacific — war on every front.
Turning Points of WWII
Stalingrad, Midway, D-Day — the tide turns.
Hiroshima & the End of WWII
The atomic bomb and the dawn of a new era.