By following Ieyasu, Masamune prioritized finding an opportunity to conquer the country in the future; he first aimed to retrieve his former territory by invading the land of the Uesugi clan, in order to acquire a total territory worth 1,000,000 koku with his own hands, which was the amount promised in the "Assurance of Hyakumangoku."
政宗は家康に従って後の天下取りの機会をうかがうことを優先し、旧領である上杉領に進攻し100万石のお墨付き分の領地を自らの手で獲得することを狙った。