Sadamori and Hidesato's army gave chase and engaged Masakado's army in Kawaguchi, Shimosa Province; Masakado himself was at the battlefront and fought bravely, causing Sadamori and Hidesato to waver, but the numerically superior Imperial forces gained the advantage over Masakado's army with the passage of time, and Masakado was eventually forced to retreat.
貞盛・秀郷軍はこれを追撃し下総国川口にて将門軍と合戦になり将門自ら陣頭に立って奮戦し貞盛・秀郷らもたじろぐが、時が経つにつれ数に勝る官軍に将門軍は押され、ついには退却を余儀なくされた。