In the Battle of Okehazama, he defeated the Imagawa clan that was Shugo (Military Governor) of Suruga Province and that intruded Owari Province, formed an alliance with the Tokugawa clan of the adjacent province, Mikawa Province, expanded its influence to Mino Province and Ise Province, went to the capital (Kyoto) and intervened in the race for successor of the Ashikaga Shogun family.
さらに尾張へ進出してきた駿河守護の今川氏を桶狭間の戦いで破り、隣国三河国の徳川氏と同盟を結ぶことによって勢力を伸ばし、美濃国、伊勢国へ勢力を広げ、ついには上洛し足利将軍家の後継争いに介入するようになる。