To prevent Koga-kubo and the Gohojo clan from joining forces, Yoshiaki decided in 1538 to lead the armies of Nobumasa MARIYA, Yoshitaka SATOMI, and other feudal lords from the Boso Peninsula into a decisive battle against the allied forces of Ujitsuna HOJO and Haruuji ASHIKAGA.
義明は古河公方と後北条氏が結びつくのを食い止めるため、1538年に真里谷信応や里見義堯ら房総の諸大名による軍勢を率いて北条氏綱・足利晴氏連合軍との決戦を決意する。