The Ouchi camp spied out the Otomo camp and embarrassed them, confused the Otomo camp by sending false reports to them -- Then, by taking the advice of Tomoyasu SADA, jito (Steward) in Usa-gun County and the head of the Sada clan, the Ouchi clan went over Sada, and in the early morning on May 28, 1534, went through to the Seiba ga haru field and made a surprise attack on the Otomo camp hidden in Mt. Omure.
大内軍は間者を用いて大友軍の動きを調べ、動向を手の内にしたり、虚報を流して大友軍を翻弄したうえ、宇佐郡地頭の佐田氏の主、佐田朝泰の進言を容れ、佐田越えののち4月6日早朝、勢場ヶ原に抜け、大村山に籠もる大友軍の奇襲を図った。