This internal discord and a move by Tanemune to offer Sanemoto DATE, his son and the younger brother of Harumune, to the Uesugi clan of Echigo Province for adoption triggered the Tenbun War, in which the Tanemune party that promoted the adoption and the Harumune party that opposed to it confronted each other.
そして、晴宗の弟である伊達実元の越後国上杉氏に入嗣させることを画策することが引き金となり、入嗣を推進する稙宗派と反対する晴宗派の間で天文の乱が勃発。