After eliminating anxiety about being attacked from behind by allying himself with the neighboring Imagawa and Gohojo clans, Shingen invaded Shinano and clashed with the Uesugi clan of Echigo over the possession of the northern Shinano region (the Battle of Kawanakajima).
信玄は隣国の今川氏、後北条氏と同盟を結んで後顧の憂いを無くして信濃侵攻を進め、北信濃地域の領有を巡って越後の上杉氏と衝突した（川中島の戦い）。