Rumania – Battle of Casin (until January 16, 1917): Allies eventually check Archduke Joseph’s 4-division advance along three Carpathian valleys.
Germany: Holtzendorff memo urges unrestricted U-boat war, can force England to peace table in 5 months ie before August 1 1917 and harvest if begun February 1.
Adriatic: 4 Austrian destroyers raid Otranto Barrage (night December 22-23): only 1 drifter damaged but 2 French destroyers hit, 2 Italian damaged plus one in collisions.
Britain: New Shipping Ministry orders five types of standard merchant ship (3,000-8,000t) until April 1917.
Austria: Count Czemin succeeds Baron Burian as Foreign Minister.