IS suffers a series of defeats in both Iraq and Syria.
Jabhat al-Nusra and other rebels detonate explosives under Aleppo's Air Force Intelligence's headquarters. The group's military chief, Abu Homam al-Shami, is killed, along with three other senior members, in an airstrike.
The UN and a global alliance of agencies, including Oxfam and Save the Children, say 2014 was the worst year of the conflict yet, and accuse members of the international community of failing victims and doing little to mitigate the humanitarian disaster in Syria.