The western army lead by Mitsunari ISHIDA first tried to gain ascendancy over various Daimyo who were on Ieyasu's side, in the territories in the vicinity of the capital to conquer their territories.
石田三成ら西軍は、まずは畿内を制圧すべく、家康方についた畿内の諸大名の制圧に務めた。