World War I (1914–1918) was a global conflict that began in Europe and quickly pulled in major powers across the world. The war reshaped borders, destroyed empires, and set the stage for future wars in the 20th century.

The fighting started after the assassination of Archduke Franz Ferdinand in 1914. Alliances triggered rapid escalation between the Allied Powers and the Central Powers. Millions of soldiers mobilized within weeks.

The United States entered the war in 1917, boosting Allied strength. The conflict ended in 1918 with an armistice, followed by the Treaty of Versailles in 1919. World War I caused massive casualties and left deep political tensions behind.