In order to avoid pressure from the Shimazu clan, Yoshishige OTOMO in Bungo Province asked for the help of Hideyoshi HASHIBA, who had suppressed Kinki, Shikoku, and Chugoku regions aiming at the unification of the whole country.
豊後国の大友義鎮は、島津氏の圧迫を回避するため、当時近畿、四国、中国地方を平定し天下統一の道を歩んでいた羽柴秀吉に助けを求める。