World War I began after the assassination of Austrian archduke Franz Ferdinand by South Slav nationalist Gavrilo Princip on June 28, 1914.

What was the first declaration of war on what date?

WarDeclarationDate of declarationWorld War IDeclaration of War upon GermanyApril 6, 1917Declaration of War upon Austria-HungaryDecember 7, 1917World War IIDeclaration of War upon JapanDecember 8, 1941

Which country was defeated after the first world war?

The war pitted the Central Powers—mainly Germany, Austria-Hungary, and Turkey—against the Allies—mainly France, Great Britain, Russia, Italy, Japan, and, from 1917, the United States. It ended with the defeat of the Central Powers.