Nanbu clan
In 1582, with the death of Nanbu Harumasa, the Nanbu clan collapsed into numerous competing factions. The 25th hereditary clan chieftain, Nanbu Harutsugu, was a boy of 13 and soon died under uncertain circumstances, and the Kunohe branch of the Nanbu clan under the warlord Kunohe Masazane began to expand its influence over the Sannohe main branch. This provided an opportunity for Ōura Tamenobu to declare that the western Nanbu territories under his control would henceforth be independent of Nanbu rule. Proclaimed a traitor by the Nanbu clan, rivals Nanbu Nobunao and Kunohe Masazane both called for Tamenobu's death. Tamenobu, realizing that he would need to solicit outside help, approached the Mogami clan for an introduction to the regime of Toyotomi Hideyoshi. Tamenobu initially departed by boat from Ajigasawa, but inclement winds blew the boat north as far as Matsumae. He made attempts to reach Hideyoshi overland in 1586, 1587 and 1588, but was blocked each time by hostile forces in the territories to the south of Tsugaru.