Having subjugated much of Honshū and Shikoku, Hideyoshi turned his attention to the southernmost of the main Japanese islands, Kyūshū.

Battles had raged for the previous few years between the daimyō of Kyūshū, and by 1585 the Shimazu family of Satsuma were the primary power on the island.

The Ōtomo were supported by armies under Sengoku Hidehisa, Sogō Masayasu, and Chōsokabe Motochika a major Shikoku lord who had been defeated by Hideyoshi the previous year, and had thus joined him.

Hashiba Hidenaga, half-brother to Hideyoshi, landed to the south of Bungo, attacking the Shimazu at Takajō, on Kyūshū's eastern coast, in 1587.

Meanwhile, Hideyoshi took his own forces down a more westerly route, attacking Ganjaku Castle in Chikuzen province, which was held by the Akizuki clan.