18 December

Western Front

 * Indian troops begin an attack on the Germans round Givenchy (La Bassée); a five days' battle commenced.
 * French pressure towards Péronne.

Eastern Front

 * Galicia: Austrians recover Lupkow Pass over the Carpathians.

Naval and Overseas Operations

 * German cruiser SMS Friedrich Karl reported lost in Baltic.

Political

 * Egypt: Hussein I proclaimed Sultan.
 * Meeting of three Scandinavian Kings at Malmo.
 * Great Britain: Conviction of Adolf Ahlers quashed.