In April 1556, the father-in-law Dosan SAITO who was a supporter of Nobunaga defeated and died in a battle against legitimate son Yoshitatsu SAITO, and Tatsunari took up arms against Nobunaga with Hidesada HAYASHI, Michitomo HAYASHI and Katsuie SHIBATA to embezzle Shinogi and Sango which were the land directly controlled by Nobunaga.
弘治(日本)2年（1556年）4月、信長の支援者であった岳父斎藤道三が嫡男斎藤義龍との戦に敗れて死去したため、達成は林秀貞、林通具、柴田勝家らを味方につけて信長に対して挙兵し、信長の蔵入地である篠木三郷を横領しようとした。