When TAIRA no Masakado raised an army in 939 and conquered eight provinces in Kanto (Johei and Tengyo War/TAIRA no Masakado's War), he formed a coalition with TAIRA no Sadamori and attacked Sashima-gun in the Shimofusa Province, which was the base of Masakado, in March 940, next year, and suppressed the turmoil.
天慶2年（939年）平将門が兵を挙げて関東8か国を征圧する（承平・天慶の乱平将門の乱）と、平貞盛と連合し、翌天慶3年（940年）2月、将門の本拠地である下総国猿島郡を襲い乱を平定。