The Republic of Serbian Krajina or Serb Republic of Krajina ( / "Republika Srpska Krajina" or РСК / RSK), ), known as Serb Krajina ( / "Srpska Krajina") or simply Krajina, was a self-proclaimed Serb proto-state, a territory within the newly independent Croatia (formerly part of Yugoslavia), which it defied, active during the Croatian War (1991–95).