3 September

Western Front

 * Germans reach and begin to cross the Marne: they occupy line Ville sur Tourbe-River Suippe-Chateau Thierry.
 * Germans evacuate Lille.

Eastern Front

 * Lemberg, capital of Galicia, occupied by the Russians, who capture much booty.

Naval and Overseas Operations

 * HMS Speedy destroyed by a mine.

Political

 * Rome: election of Pope Benedict XV.
 * Albania: Prince Wilhelm of Wied leaves.