He succeeded the policy of Shingen, who broke up Ko So Sun Sangoku Domei (tripartite alliance of Kai, Sagami and Suruga) because of a conflict with Echigo, invaded Suruga and put the strategy to conquer westward into action.
越後との対立から甲相駿三国同盟を破棄し駿河侵攻、西上作戦を行い三河に進出した信玄の方針を継承した。