[1] He was renowned as a great general, who managed to subjugate Kyushu through the deft maneuvering of his three brothers.

On his coming-of-age (genpuku), he took the name of Tadayoshi(忠良) but after receiving a kanji from the shōgun Ashikaga Yoshiteru, changed to Yoshitatsu (義辰).

Working together with his brothers Yoshihiro, Toshihisa, and Iehisa, he launched a campaign to unify Kyūshū.

By the middle of 1585, the Shimazu clan controlled; Chikugo, Chikuzen, Hizen, Higo, Hyūga, Osumi, and Satsuma,[5] most of Kyūshū with the exception of Ōtomo's domain and unification was a feasible goal.

Hideyoshi mobilised a force of 200,000 soldiers and 20,000 pack animals, transporting supplies for an even larger army of 300,000 men.

By April 1587 Hideyoshi had reached the straits at Shimonoseki, moving through Chikuzen and Chikugo to attack Yoshihisa in Higo.

The Shimazu fought well, but had few firearms and lacked discipline and training; they were steadily overwhelmed through the superior quality and quantity.

As a retainer under Hideyoshi, his younger brother Yoshihiro controlled troops, but it is believed that Yoshihisa still managed day-to-day affairs in the domain.

[1] Yoshihisa's knowledge of culture is not known, but after Hideyoshi granted Hosokawa Fujitaka a retirement estate at Osumi Province in 1595, Fujitaka taught him classic literatures, and Kampaku Konoe Wakihisa, who was skilled in waka and renga, is believed to have frequented Yoshihisa's house.

There are also monuments built in his memory at Kokubun, Ima Kumano Kannonji (今熊野観音寺) in Kyoto, and Koyasan.