Sumitomo made several attacks as a conditional strike for merits against the Imperial Court in several places in Saigoku (the western part of Japan), but he was defeated and killed by the Imperial army which was able to concentrate its military power in Saigoku after putting an end to the war against TAIRA no Masakado.
西国各地を襲撃して朝廷に勲功評価の条件闘争を仕掛け、これを脅かしたが、平将門の乱を収拾して西国に軍事力を集中させた朝廷軍の追討を受けて滅ぼされた。