From the beginning of the Sengoku period (period of warring states), the Ouchi clan which had been influential in Buzen and Chikuzen in the northern part of Kyushu placed the many regions from Iwami and Aki in the east to Chikuzen, Hizen, Chikugo and so forth in the west under its control.
戦国初期より、九州北部の豊前、筑前に勢力をもっていた大内氏は、東は石見・安芸、西は筑前、肥前、筑後など、多くの地域を勢力下においていた。