At the beginning of the Sengoku Period, battles were repeated by three clans since the Heian Period, the Shoni clan, the Otomo clan, and the Shimazu clan to protect their interests and by kokujin gozoku in each country who were formerly jito to become independent.
戦国時代当初、少弐、大友、島津の三氏は権益を守るべく、また地頭出自の諸国の国人豪族は自立するべく、戦いが展開していった。