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Why did one assassination trigger a world war? Like a quarrel that spreads as others take sides, Europe was already divided. Britain and France competed with rising Germany and Italy for colonies and markets. The Triple Alliance united Germany, Austria-Hungary, and Italy; the Triple Entente linked Britain, France, and Russia. Both armed rapidly, while Austria-Hungary's control of Bosnia fueled conflict with Serbia. Then, in 1914, Serbian nationalist Gavrilo Princip assassinated Archduke Franz Ferdinand in Sarajevo. Austria-Hungary blamed Serbia and declared war. The assassination was not the whole cause. It was the spark. The war ended in 1918, leaving Europe devastated and economically weakened. The United States grew stronger and became a creditor. In 1919, the Treaty of Versailles imposed harsh terms on Germany; old empires collapsed and Europe's map changed. Years of rivalry and sides-taking made the assassination ignite a war that weakened Europe and raised America.