World War I
Learn about World War I — the 'Great War' that killed 20 million people, destroyed empires, and reshaped the world from 1914 to 1918.
World War I (1914–1918) was the first global industrial war and one of the most catastrophic events in human history. It killed approximately 20 million people (military and civilian), wounded 21 million more, destroyed four empires (German, Austro-Hungarian, Ottoman, Russian), and created the conditions for World War II, the Russian Revolution, and the modern Middle East.
The war's causes were deeply rooted in the rivalries of the European great powers: alliance systems that linked nations in mutual defense obligations, imperial competition for colonies and markets, an arms race (particularly the Anglo-German naval rivalry), and nationalist tensions in the Balkans. The assassination of Archduke Franz Ferdinand of Austria-Hungary on June 28, 1914, activated these interlocking tensions, and within six weeks, all the major European powers were at war.
The Western Front became a nightmare of trench warfare — four years of stalemate in which millions died for gains measured in yards. New technologies — machine guns, poison gas, tanks, aircraft, submarines — made this war unprecedentedly destructive. The entry of the United States in 1917 tipped the balance. Germany sought an armistice on November 11, 1918. The peace settlement, centered on the Treaty of Versailles, imposed harsh terms on Germany that sowed the seeds of the next global conflict.
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 Treaty of Versailles
The peace that planted the seeds of the next war.