What is the major reason that chief joseph gives for his surrender to u. s. forces?

Chief Joseph, also known as Hin-mah-too-yah-lat-kekt, is known to be the leader of the Wal-lam-wat-kain which is native American tribe. The main reason why he has surrendered to the U.S forces is that his leaders were already dead, his people are having a difficult time surviving, and he was also tired of fighting. Hope this helps.