When Ieyasu TOKUGAWA of the eastern military group won the Battle of Sekigahara, many daimyo families of the western military group lost their positions as well as their territories or were forced to reduce their territories, producing lots of 牢人.
関ヶ原の戦いで東軍の徳川家康が勝利すると西軍についた大名の多くが取り潰されるか、大幅な領地の減封を受け、これによって大量の牢人が生じた。