It began Process_start as a series of political Social_event and military confrontations Hostile_encounter , between Julius Caesar ( 100–44 BC ) , his political supporters ( broadly known as Populares ) , and his legions , against the Optimates ( or `` Boni '' ) , the politically conservative and socially traditionalist faction of the Roman Senate , who were supported Supporting by Pompey ( 106–48 BC ) and his legions .