How close did the Shimazu come to unifying Kyushu?

Very close. By 1587, the Shimazu had defeated or subjugated almost every other major power on Kyushu, including the Otomo and the Ryuzoji. Only Hideyoshi's military intervention with an overwhelming force (estimated 200,000-300,000) stopped the Shimazu from completing their conquest. Had Hideyoshi not intervened, the Shimazu would have controlled the entire island.

What happened after Yoshihisa submitted to Hideyoshi?

Yoshihisa formally surrendered to Hideyoshi in 1587 in a ceremonially dramatic meeting. He was allowed to retain much of his domain — a generous settlement reflecting Hideyoshi's pragmatism. The Shimazu participated in Hideyoshi's Korean invasions (1592, 1597). After Hideyoshi's death, the Shimazu sided with the Western Army at Sekigahara (1600) but survived the defeat relatively intact, retaining Satsuma domain into the Edo period.

Shimazu Yoshihisa: The Lord Who Nearly Unified Kyushu

Shimazu Yoshihisa came closer to unifying a major Japanese island than almost any other Sengoku warlord outside the great triumvirate of Nobunaga, Hideyoshi, and Ieyasu. He controlled most of Kyushu — Japan’s southernmost main island — before Toyotomi Hideyoshi’s overwhelming intervention stopped him in 1587.

The Shimazu Base

The Shimazu were the dominant clan of Satsuma province in southern Kyushu — one of Japan’s oldest and most militarily capable warrior houses. They had governed Satsuma since the Kamakura period. When Yoshihisa took control of the clan in 1566, he inherited a powerful military tradition and a stable territorial base. [history]

The Kyushu Conquests

The mid-16th century Kyushu balance of power involved three major clans: the Shimazu in the south, the Otomo in the northeast, and the Ryuzoji in the northwest. Yoshihisa systematically dismantled his rivals.

Battle of Mimikawa (1578): The Otomo lord Sorin launched a major invasion of Shimazu territory with a large army. Yoshihisa’s forces defeated it decisively. The Otomo power base never fully recovered. [history]

Battle of Okitanawate (1584): Ryuzoji Takanobu, the most powerful northern Kyushu warlord, led an army against the Shimazu and their allies. Ryuzoji was killed in the battle. His clan quickly collapsed. [history]

By 1587, the Shimazu controlled approximately 90% of Kyushu. Only isolated Otomo holdings in the far north remained. Japan’s southernmost major island was effectively under one warlord’s control.

Hideyoshi’s Intervention

Toyotomi Hideyoshi had been consolidating power on Honshu. The emergence of a unified Kyushu under a single powerful lord was a strategic threat he could not allow. In 1587, he launched an invasion of Kyushu with an army commonly estimated at 200,000 to 300,000 — dwarfing anything the Shimazu could field. [history]

The Shimazu fought initially but the numbers were impossible. Yoshihisa submitted formally to Hideyoshi in a ceremony on Kyushu — arriving dressed as a Buddhist monk, a gesture of humility. Hideyoshi’s response was relatively generous: the Shimazu retained control of Satsuma and the adjacent provinces. [history]

Survival and Legacy

The Shimazu proved remarkably durable. They participated in Hideyoshi’s Korean invasions (1592, 1597), fighting at the Battle of Sacheon and distinguishing themselves militarily. At Sekigahara (1600), they sided with the Western Army — against Tokugawa Ieyasu. After the Eastern Army’s victory, the Shimazu faced potential elimination.

They survived. Their famous “Shimazu Retreat” at Sekigahara — withdrawing directly through the Eastern Army’s lines under fire when their position became untenable — was a costly but functional escape. Ieyasu accepted their eventual submission. [history]

The Shimazu retained Satsuma domain into the Edo period, remaining one of Japan’s most powerful tozama (outside) lords. It was Satsuma samurai — the Shimazu’s retainers’ descendants — who formed one of the two main forces (alongside the Choshu domain) that overthrew the Tokugawa shogunate in the Meiji Restoration of 1868. The clan that Yoshihisa led outlasted the system that stopped his conquest by nearly 300 years.