12 September

Western Front

 * Troyon: Germans compelled to raise siege.
 * Luneville reoccupied by the French.
 * Belgian sortie from Antwerp threatens German communications.

Eastern Front

 * Galicia: End of Battle of Grodek and Rava-Ruska: total defeat of Austrians; Grodek captured.
 * Poland: Austrians try to cross the San under heavy fire.

Southern Front

 * Syrmia: Serbians occupy Jarak.

Naval and Overseas Operations

 * East Africa: Germans defeated near Kisi.