23 August

Western Front

 * Namur falls.
 * Battle of Mons begins: general German attack on the French from Charleroi to Dinant.
 * French begin to fall back from Sambre and Meuse; also in northern Alsace.

Eastern Front

 * East Prussia: Germans evacuate Insterburg; at the Battle of Frankenau, Germans driven back.
 * Galicia: Russians take Brody and Tarnopol.

Asiatic and Egyptian Theatres

 * Tsing-tau blockaded and bombarded by the Japanese.

Political

 * Japan declares war on Germany.
 * Germany: General Hindenburg receives command in East Prussia.