Western Front
Five Jasta 2 fighters (led by Richthofen) shoot or force down 5 DH2s. RFC observers engage 85 targets including destroying 3-gun anti-aircraft batteries, takes 741 photos.
Eastern Front
German Navy airships
L-35 (Ehrlich) and
L-38 (Dietrich) arrive at Wainoden for Operation Eisernes Kreuz (Iron Cross), a raid on Petrograd advocated since early 1915 by Grand-Admiral Prince Heinrich, C-in-C Baltic Fleet.
Romania: Russian 12th Cavalry Division reaches Odobesti 15 miles northwest of Focsani (after 450-mile ride without losing a single horse).
Galicia: Severe fighting west of Brody.
Southern Front
Fierce local encounters Cherna bend (Monastir).
Asiatic and Egyptian Theaters
Turks evacuate El Arish (northern Sinai) and fall back 20 miles south-east of Magdhaba.
Naval and Overseas Operations
Mediterranean: British troopship
Itonus is sunk by the German submarine
SM U-38 off Malta, resulting in 5 crew deaths:
http://imgur.com/0j816LL
East Africa: Germans retire from Nangadi (East Africa).
Political, etc.
Germany: Chancellor von Bethmann-Hollweg comes under sustained pressure from German Army and Navy for unlimited U-boat warfare without delay (December 20-26). Ludendorff urges immediate unrestricted U-boat war in view of Lloyd George reply.
German War Loan M 535,000,000.
United States: U.S. War Department orders 4000 Vickers machine guns for the cost of $5.5 million ($121 million today).
President Wilson's Peace Conference Note handed to Belligerents.