It all started with Tigerstar.
He thought he could take over the forest with the help of RiverClan and BloodClan (A giant group of twoleg place cats). He grouped together TigerClan. While Firestar and Tallstar created Lionclan. At the gathering when all clans were there Tigerstar claimed the forest would be his. So that made Scourge ANGRY. So Scourge murdered him infront of all of the clans. So then all clans joined together and attacked BloodClan. The clans were STILL out numbered (ALL FOUR CLANS!). But in the end the clans won and Firestar killed Scourge.