In 1578, when Kenshin UESUGI died, Kagekatsu UESUGI, his nephew, and Kagetora UESUGI (Saburo HOJO, legendary Ujihide, as his name), his adopted child and the younger brother of Ujimasa, started fighting over the succession of the reigns (the Otate War) (Although Ujihide HOJO had been identified as Kagetora, a new theory suggests that Ujihide is not Kagetora but the younger brother of Ujishige HOJO who served as the lord of the Edo Castle).
天正6年（1578年）、上杉謙信が死去すると、その後継者をめぐって謙信の甥・上杉景勝と氏政の弟で謙信の養子・上杉景虎（北条三郎、名は氏秀と伝わる。しかし氏秀は北条氏繁の弟で江戸城主であり景虎とは別人との説がある）の後継者争いである御館の乱がおこった。