The Fire Nation Civil War began when Firelord Bush started to drink crazyily.
The Fire Nation was having a time of peace, until Bush's wife began to cheat on him with the Earth King. Because Bush sucked at Firebending while the Earth King rocked, he could not kill him. So, he ordered for his wife to "disappear". Without a motherly figure, his son, became one of the worst firelords in history. But, Bush didn't care he just started drinking a lot. He also visited lots of Bars, eventually his people got fed up and rebelled. The rebel army soon controlled almost all of the Fire Nation except a little bit of the big island and Capital City. Bush, then died because he was drinking too much.
Bush's son Pikachu took the throne and kicked rebel butt. He eventually went too far killing innocent people, but he did end the war.