In 1510, Tamekage had Akisada UESUGI, Kanto Kanrei (a shogunal deputy for the Kanto region), killed in the Battle of Nagamorihara, allowing him to hold sway in Echigo Province.
永正7年（1510年）には関東管領上杉顕定をも長森原の戦いにおいて敗死させて越後一国に覇を唱えた。