When the Battle of Sekigahara, in which Mitsunari and so on raised an army, occurred in 1600, Hideyori was placed under the protection of Terumoto MORI, who was a member of Gotairo and was set up as the leader of the Western Camp.
慶長5年（1600年）に三成らが家康に対して挙兵する関ヶ原の戦いが勃発すると、秀頼は西軍の総大将として擁立された、五大老毛利輝元の庇護下におかれた。