The changing of the tides in the Kanmon straits is very strong, and the Taira navy, who had a thorough understanding of the tides there, was able to ride the rapid tidal current and rain down arrows on the enemy, and kept pushing back the Yoshitsune's army, the warriors from the east Japan, who were unused to fighting at sea.
関門海峡は潮の流れの変化が激しく、水軍の運用に長けた平氏軍はこれを熟知しており、早い潮の流れに乗ってさんざんに矢を射かけて、海戦に慣れない坂東武者の義経軍を押しまくった。