This chapter summarizes the origins and evolution of armed conflicts active in 2015, as recorded by the Uppsala Conflict Data Program (UCDP). Descriptive profiles are provided of active armed conflicts that reached the level of war either in 2015 or in one or more previous years. 1 War is defined as an armed conflict that resulted in at least 1,000 battle-related deaths within a calendar year. This chapter is compiled based on information published on the UCDP website and included in various UCDP datasets (www.ucdp.uu.se). The details about armed conflict activity in 2015 also draw on the most recent publications about UCDP data (Melander, Pettersson, and Themnér 2016).