Shonai Rebellion (庄内の乱)
The Shonai Rebellion occurred in 1599 in Shonai, Hyuga Province (the present-day Miyakonojo City, Miyazaki Prefecture and surroundings) between the Shimazu clan and the Ijuin clan, the chief vassal of the Shimazu clan. This rebellion, which was the largest revolt within the Shimazu clan, was eventually resolved through the mediation of Ieyasu TOKUGAWA. The rebellion is also considered the reason that the Shimazu clan couldn't send a large force to the Battle of Sekigahara, because the rebellion occurred immediately after the Keicho Campaign and just before the Battle of Sekigahara.
Murder of Tadamune IJUIN
On April 4, 1599, Tadamune IJUIN was killed by Tadatsune SHIMAZU's sword at the Fushimi Shimazu residence. Tadamune IJUIN was Yoshihisa SHIMAZU's chief vassal and an important follower who worked for the Shimazu clan in the conquest of Kyushu. When Hideyoshi TOYOTOMI started his conquest of Kyushu, he recognized the difference in military force between the Toyotomi clan and the Shimazu clan and therefore recommended an early surrender. After the surrender, he made himself a hostage and went to Kyoto for post-war activities; that contributed to the continuance of the Shimazu clan. Therefore, he was recognized as the major vassal of the Shimazu family, and received one county directly from Hideyoshi as part of the post-war treatment.
In 1594, a survey was conducted within the Shimazu family territory, and the Ijuin clan received Miyakonojo, the land worthwhile 80,000 koku of rice, with a certificate from Hideyoshi TOYOTOMI. The Hokugo clan originally held Miyakonojo, but since Tadayoshi HOKUGO was underage and there weren't enough soldiers for the invasion of Korea, the clan was transferred to Kedoin and the size of its territory was reduced to 37,000 from 69,000 koku. Tadamune received direct orders from Hideyoshi and became the manager for the enfeoffment distribution after the survey. Consequently, discontent within the Shimazu family was concentrated on Tadamune and he was called the 'flatterer, crafty person' who was disturbing the Shimazu family. The residence held by the Ijuin clan in Fushimi was larger than the residence of the main family of the Shimazu clan. This led to rumors in the domain that the Ijuin clan was trying to take over the main family of the Shimazu clan.
Tadatsune SHIMAZU was the third son of Yoshihiro SHIMAZU, who was a younger brother of Yoshihisa SHIMAZU, the head of the main family of the Shimazu clan. Because Yoshihisa had no sons and Tadatsune's elder brothers Tsurujumaru and Hisayasu died young, he married Yoshihisa's third daughter, Kameju, and became a successor as the head of the Shimazu clan.
According to Nisshu Shonai Gunki, there is an entry stating that Mitsunari ISHIDA or Ieyasu TOKUGAWA told Tadatsune, who had returned from Korea after the death of Hideyoshi TOYOTOMI, that Tadamune IJUIN was thinking of rebellion, but there is no other historical evidence of the same era to prove it. As the successor to the head of the Shimazu clan, Tadamune IJUIN recommended Yoshihisa's second daughter Shinjo's husband, Akihisa SHIMAZU; that might be another reason for Tadatsune to hate Tadamune. Moreover, the domain failed in sending sufficient supplies to the troops that Tadatsune led during the Korean invasion. Tadamune didn't go to Korea, so he was blamed for the insufficient supplies for Tadatsune and was borne a grudge against by the other vassals of the Shimazu clan. Therefore, Tadatsune called Tadamune during the absence of Yoshihisa and Yoshihiro, and killed him.
Although he was a vassal of the Shimazu clan, the act of killing Tadamune, who had been given Miyakonojo, the land worthwhile 80,000 koku of rice, with a certificate, could have been taken as an act of treason against the central government. Tadatsune was under suspension at Jingo-ji Temple on Mt. Takao. Takamune's wife and children were sent to Tofuku-ji Temple. Ieyasu TOKUGAWA, who held the real political power at that time, supported Tadatsune's actions by approving a lord's punishing his vassal who rebelled, and as a result, Tadatsune returned to the Shimazu residence.
Yoshihisa explained to Mitsunari ISHIDA that Takamune's assassination was solely Tadatsune's decision and he was not involved in any way. However, although it was written later, 'Shonai Jinki' (Shonai war chronicle) has an entry stating that Yoshihiro and Tadatsune had conspired together while Yoshihisa gave his consent to the plan. In the next month, on March 3, Yoshihisa blocked the roads to Miyakojiro and took a sworn oath from the Shimazu clan vassals not to support Tadamasa.
Tadamasa IJUIN besieged
While Tadamune's legitimate child, Tadamasa IJUIN, was hunting at Mt. Ogawara near Miyakojiro, he received the message that his father had been killed and immediately rushed back. After discussions with his family and vassals, his uncle Shinemon IJUIN argued that they should secure their lands, but the visiting warrior, Eisen SHIRAISHI, who had been a monk at Kishu (the present-day Wakayama Prefecture) Negoro-ji Temple and was the head monk at Kosai-ji Temple, asserted that they should resist to the last. Eventually, Eisen's proposal was accepted and it is said that the decision was made to rebel against the main family of the Shimazu clan.
However, Tadazane sent a letter to Tadatomo KAWAKAMI on June 18 stating, 'I immediately paid a visit to the residence of Mr. Yoshihisa after my father's death. I said that I was ready to follow any orders of Mr. Yoshihiro and Mr. Tadatsune, but Mr. Yoshihisa was not convinced at all and prohibited travel to Shonai. It seems that I am being treated like my father and the boundary of the territories is set on fire,' whereby he claimed that Yoshihisa was going to demolish the Ijuin clan. Tadazane asked for Yoshihiro to mediate between them in this letter, but Yoshihiro advised Tadazane to surrender.
Miyakonojo was an impregnable fort, having Miyakonojo as a main castle, which was protected by 12 outer castles: Tsuneyoshi-jo Castle, Umekita-jo Castle, Shiwachi-jo Castle, Kajiyama-jo Castle, Katsuoka-jo Castle, Yamanokuchi-jo Castle, Gassan Hyuga-jo Castle, Yasunaga-jo Castle, Nonomidani-jo Castle, Sueyoshi-jo Castle, Yamada-jo Castle, and Takarabe-jo Castle. Tadazane strengthened each outer castle, in which he positioned his family and vassals to increase the defenses. According to the Shonai Gunki, Tadazane's forces numbered 20,000, but actually they were about 8,000. According to the 'Takajirocho history,' those including Kiyomasa KATO and Suketaka ITO, who shared the borders with the Shimazu clain, provided support including materials in secret, although they are not counted as a direct military power. The Shimazu clan protested to the two lords.
Participation of Tadatsune SHIMAZU in battle
Tadatsune obtained permission from Ieyasu TOKUGAWA and returned to his province in order to quell the rebellion by himself. He left Kagoshima in June, placed his main base at Tumakirishima Kongobussa-ji Temple, and attacked Shonai. The Shimazu clan family and main vassals joined the attack. Particularly, since it was a chance for the Hokugo clan to regain its former territory, all involved from his clan worked hard. According to the Shonai Gunki, Tadatsune's forces numbered approximately 100,000, but actually they amounted to about 30,000 to 40,000.
Ieyasu TOKUGAWA sent his vassal, Naotomo YAMAGUCHI, as a messenger and asked the parties to reconcile but failed. He also asked the various feudal lords in Kyushu to support the Shimazu clan.
Tadatsune captured Yamada-jo Castle in the beginning of a war. He then captured Tsuneyoshi-jo Castle, which was not followed by any achievements and the battle reached a stalemate. Afterward, Tadatsune set camp in Morita between Nonomitani and Shiwachi, and laid siege to Shiwachi-jo Castle. Since Tadamasa tried to send food to Shiwachi-jo Castle but couldn't succeed, the starvation within the castle was severe.
On the other hand, those including the resourceful general Eisen SHIRAISHI on Tadamasa's side fought actively, so on the Tadatsune's side had heavy casulatlies. Yoshihisa also went into battle and attacked Takarabe-jo Castle (Takarabe, Kagoshima Prefecture) but couldn't capture it.
The surrender of Tadamasa IJUIN
Ieyasu sent Naotomo YAMAGUCHI again as a messenger and mediated a peace between the two sides.
Naotomo had a letter of proof from Yoshihisa and Tadatsune stating, 'If Tadamasa surrenders, you will continue to be vassals as before.'
This was shown to Tadamasa in order to prompt his surrender.
On March 20, 1600, Shiwachi-jo Castle was surrendered. The other outer castles were then surrendered in turn, and Tadamasa accepted Ieyasu's peace terms and surrendered on April 28. After surrendering, the fief of Tadamasa was transferred to Ei, the land worthwhile 10,000 koku of rice, and later transferred to Chosa, the land worthwhile 20,000-koku of rice. Miyakonoshiro was returned to the original lord the Hokugo clan, which was the end of the rebellion.
The next year in 1601, the Shimazu family issued a ban on the Ikko sect (a formal notice with the names of Yoshihisa, Yoshihiro and Tadatsune), and ultimately this became the cause of the later 'hidden chanting.'
According to an opinion, this policy was related to the fact that Tadamune was a devoted Ikko believer.
The decline of the Ijuin clan
Even after the rebellion ended, Tadatsune was still wary of Tadamasa. In fact, Tadamasa had sent a secret messenger to Kiyomasa KATO in Higo Province to ask for his help in vengeance. However, Jinkichi IJUIN, who was given the secret message, passed it on to Tadatsune. Not only Tadatsune but also Ieyasu was angry with Tadamasa; however, they decided to forgive him because he could no longer be a threat to the Shimazu clan.
But after the Battle of Sekigahara, in 1602, Tadatsune ordered Tadamasa to accompany him to the capital and shot him to death during a hunt in Nojiri, Hyuga Province. The same day, Tadamasa's mother and three brothers were also killed.