User blog comment:B214/Question and Answers/@comment-50.11.177.49-20130529004308/@comment-33447191-20130529013057

1. Not sure whether or not the current Maou participated in the Great War never specified.

2. We don't know all that much about the circumstances about the Old Satan Faction and the Anti-Satan Faction, but we do know that the reason most of the Devils sided with the Anti-Satan Faction was because (as you may have already known the original Maou perished along with God from the Bible in the Great War) the descendants of the original Maou (namely: Katerea Leviathan, Shalba Beelzebub, and Creuserey Asmodeus) sought to carry on their legacy and finish the Great War but saw confrontation from a certain group of Devils which caused a huge conflict between the Devils. Following the defeat of the descendants who were forced to retreat to the back part of the Underworld, their names became titles for the new supreme rulers of the Devils.

Basically, everyone was sick of fighting after the Great War but the descendants wanted to finish what they started... One thing led to another.... and that's that.