Western Front
Battle of Verdun: French 133rd Division (Passaga) claims to clrecapture Bezonvaux and Hardaumont. Again, most of the militarily significant territory remained in German hands. German counter-attack regains Les Chambrettes Farm on December 17. French further claim that 11,000 prisoners and much war material are captured.
{Copied verbatum, cause even if not accurate,the comparison is cool} German lines being bombarded by French artillery at Vacherauville, France:
http://imgur.com/kxECDqA While I cannot say for certain, this might be the same view today via Google Earth:
http://imgur.com/hRv6PF8
Eastern Front
Pripet: Russian positions between Kovel and Lutsk captured (restored on December 18).
Dobruja: Sakharov retreats north on Braila (until December 20).
Southern Front
Greece: Greek Army begins evacuation of Thessaly under Allied supervision (Anglo-French control officers).
Naval and Overseas Operations
East Africa: General Cunliffe's Nigerian brigade reaches Dar-es-Salaam.
Political, etc.
Russia: Russia dismisses German peace offer, stating it was a “sensational act of publicity calculated to prepossess the neutral powers.”
Germany: Friedrich Ernst Dorn, German physicist who discovered radium emits a radioactive substance, passed away:
http://imgur.com/ZpQqfwG
Prussian General Max von Fabeck commits suicide after he was evacuated from the front due to serious illness:
http://imgur.com/rVbRgy5
United Kingdom: British news film “Topical Budget,” showing blind soldiers being taught to become masseurs, among other news:
http://film.iwmcollections.org.uk/record/index/5409
Ireland: Government decides to take over Irish railways, to satisfaction of Irish public.
Romania: Ion Bratianu forms Coalition Goverment, Tache Ionescu joins on December 25.
Portugal: Creation of the Portuguese Expeditionary Corps to serve in France alongside the rest of the Allies is announced.