In May 1221, when the Retired Emperor Gotoba raised an army to attack the shogunate, Shigetada joined it along with his relatives including Sakon MIZUNO (the founder of the Mizuno clan).
承久3年（1221年）5月、後鳥羽上皇が討幕の挙兵をすると重忠は水野左近（水野氏の祖）ら一族とともにこれに参じた。