In the Tenbun era, invasions of Shinano by Shingen TAKEDA, Kai Province, and of Kita Kanto (Northern Kanto) by Ujiyasu HOJO, Sagami Province, were implemented full-scale against a backdrop of Ko So Sun Sangoku Domei (tripartite of Kai-Sagami- Suruga alliance), and due to these invasions by both parties which dispatched troops to each other under the Koso Alliance (an alliance between the Takeda clan in Kai Province and the Hojo clan in Sagami Province), Kagetora was forced to take a double front strategy.
天文年間には甲相駿三国同盟を背景とした甲斐の武田信玄による信濃侵攻と相模の北条氏康による北関東侵攻が本格化しており、甲相同盟により相互に出兵した両者の侵攻により、景虎は二正面作戦を余儀なくされる。