The Battle of Kyushu (九州の役)
The Battle of Kyushu was a general name for battles between Hideyoshi TOYOTOMI (surname "Toyotomi" was bestowed on September 9, 1586) and the Shimazu clan from August and September 1586 to May and June 1587. It is also referred to as Hideyoshi's invasion of Kyushu, the subjugation of Kyushu, and the Kyushu Conquest.
Unification of Kyushu by the Shimazu clan
In Kyushu at that time, the Shimazu clan in Satsuma Province had defeated the Ito clan in Hyuga Province, the Sagara and Aso clans in Higo Province, and the Arima and the Ryuzoji clans in Hizen Province. Having also conquered the territories of local lords in Chikugo Province, where the domination by the Otomo clan had weakened as the result of the death of Dosetsu TACHIBANA, a powerful leader of the Otomo clan, the Shimazu clan was just about to establish its rule over the entire island of Kyushu. In order to avoid pressure from the Shimazu clan, Yoshishige OTOMO in Bungo Province asked for the help of Hideyoshi HASHIBA, who had suppressed Kinki, Shikoku, and Chugoku regions aiming at the unification of the whole country.
In response to this, Hideyoshi who had become a chancellor, ordered the Shimazu clan and the Otomo clan to cease fire by authority of the imperial court (sobuji rei - Peace edicts) in October 1585. However, the Shimazu clan ignored the order and continued to fight battles in order to establish its rule over Kyushu, which made Hideyoshi decide to invade Kyushu.
To finish the unification of Kyushu, the Shimazu clan started to invade Buzen, Bungo, and Chikuzen Provinces, which were territories of the Otomo clan.
The battle of Chikuzen
See the battle of Iwaya-jo Castle.
Yoshihiro SHIMAZU, who intended to establish his rule over Kyushu before Hideyoshi arrived, started to invade Chikuzen Province in June 1598 and brought the western half of the province under his control. What remained for him were Iwaya-jo Castle defended by Joun TAKAHASHI, Tachibana-jo Castle defended by Muneshige TACHIBANA, and Homanyama-jo Castle defended by Naotsugu TACHIBANA. In July, Shimazu's army attacked Iwaya-jo Castle with more than 30,000 soldiers, they struggled against the resistance of Joun TAKAHASHI, and finally managed to capture it. It was a large miscalculation for the Shimazu side because Kakuken (Satokane) UWAI was wounded and thousands of the samurai were killed. Shimazu's army made Homanyama-jo Castle fall immediately after that, but gave up Tachibana-jo Castle in order to raise the siege, and changed course to invade Bungo. At this time, Muneshige TACHIBANA ran after the Shimazu's retreating army, and retrieved Takatorii-jo Castle, Iwaya-jo Castle, and Homanyama-jo Castle.
The Battle of Bungo
On the other hand, Hideyoshi ordered the Mori clan to charge forward to Buzen in September of the same year. He also made the Sogo clan and the Chosokabe clan charge forward to Bungo, and they joined the Otomo clan against Shimazu's army sent to invade Bungo. In the beginning, the Shimazu clan had the advantage with problems in the Otomo clan, etc. Especially in the Battle of Hetsugigawa in December, Toyotomi's side led by Hidehisa SENGOKU, Assistant Deputy General suffered a crushing defeat losing powerful busho (Japanese military commanders) including Nobuchika CHOSOKABE and Masayasu SOGO.
Encouraged by their victory, the Shimazu army captured Funai-jo Castle, which had been abandoned by Yoshimune OTOMO, and besieged Nyushima-jo Castle, which was defended by Sorin. Nyushima-jo Castle managed to sustain itself using Furankiho (Ishibiya) (Ishibiya is literally, stone fire arrow) that Sorin imported from Portugal and called Kunikuzushi (literally, destroying a nation).
Mobilization of Toyotomi's army
As Sorin repeatedly encouraged Hideyoshi to move forward, Hideyoshi issued a military order to invade Kyushu in February and March 1587, and he dispatched himself in April and May. With Hideyoshi aiming for Higo and his brother Hidenaga TOYOTOMI aiming for Hyuga, Toyotomi's army advanced with an overwhelming amount of material and samurai, over 200,000 people in total. Upon sensing the landing of Hideyoshi, Shimazu's army almost abandoned northern Kyushu, and Hideyoshi captured castles ruled by the Shimazu clan instantly, partly because the rule by the Shimazu clan was nothing more than a formal rule by occupation forces. The Shimazu clan kept withdrawing, and changed course to strengthen its defense of Satsuma.
The army led by Hidenaga entered Hyuga via Bungo, and then sieged Taka-jo Castle (Niiroin) defended by Arinobu YAMADA via Agata. Yoshihiro SHIMAZU, who went to the rescue, suffered a crushing defeat and lost Tadachika SHIMAZU in the battle of Nejirozaka, and Taka-jo Castle was seized by Hidenaga. Furthermore, Hidetsugu TOYOTOMI conquered Tonokori-jo Castle and advanced to Iwamure-jo Castle on the border between Kobayashi City and Nojiri-cho. Yoshihiro stayed in Iino-jo Castle, pretending to put up determined resistance against Hidetsugu.
Meanwhile, Hideyoshi conquered Tanezane AKIZUKI's Ganjaku-jo Castle and succeeded in persuading Harunobu ARIMA in Shimabara to surrender. Tadatoki SHIMAZU abandoned Takada and withdrew to Izumi. Hideyoshi advanced to Izumi via Yatsushiro and Minamata faster than expected by the Shimazu side, and made Tadatoki SHIMAZU, the lord of Izumi-jo Castle, surrender. Hideyoshi further blew up Tadanaga SHIMAZU, and settled the headquarters of his army in Taihei-ji Temple of Sendai (Satsumasendai City). In April, Yoshihisa SHIMAZU visited Taihei-ji Temple to surrender.
Even after the surrender of Yoshihisa, Yoshihiro SHIMAZU stayed in Iino-jo Castle and Toshihisa SHIMAZU, whose adopted son-in-law, Tadachika, was killed, continued resistance. Although the Shimazu clan was finally deprived of most of its territories in Kyushu, it was granted the right to rule Satsuma and Osumi Provinces as a result of the post-war actions taken by Mitsunari ISHIDA and Tadamune IJUIN.
Hideyoshi intended to provide the whole Osumi Province to Motochika CHOSOKABE who lost his heir Nobuchika in the Battle of Hetsugigawa, but Motochika firmly declined the offer.
Furthermore, Tanezane AKIZUKI in Chikuzen who colluded with the Shimazu clan was transferred to Hyuga, and Sumimasa FUKABORI, who repeatedly attacked Nagasaki Port and charged transport dues on the early European ships because of his confrontation with the Omura clan, was punished by depriving him of his territory for violation of Ban on Piracy.
Since Hideyoshi TOYOTOMI suppressed Saigoku (western part of Japan - especially Kyushu, but ranging as far east as Kinki), he started to contact Korea and Ryukyu to make them subordinate states. He also aimed to suppress the remaining Togoku (the eastern part of Japan, particularly the Kanto region). He turned his fire on the Gohojo clan in Kanto and the Date clan in Oshu (Northern Honshu, the region encompassing Mutsu and Dewa provinces).