Location: Miyakonojō and its environs in Hyūga Province
Synopsis: Following the Subjugation of Kyūshū by Toyotomi Hideyoshi, a chief retainer of the Shimazu clan named Ijūin Tadamune was sent to Fushimi to serve as a representative of the clan in dealings with the Toyotomi. His work supporting the Toyotomi stirred resentment which led to his slaying by Shimazu Tadatsune. His son, Ijūin Tadazane, sought to reconcile with the Shimazu but, after being rejected, he rebelled. Mediation by Tokugawa Ieyasu led to a surrender by the Ijūin and settlement with the Shimazu. Several years later, however, Tadazane was shot and killed owing to ongoing resentment and distrust by the Shimazu toward the Ijūin.
The Shōnai Rebellion occurred in 1599 in Shōnai in Hyūga Province during the period after the Keichō Campaign on the Korean Peninsula and before the Battle of Sekihahara in 1600. The conflict was waged between the Shimazu clan and the Ijūin clan as senior retainers of the Shimazu. This marked the most significant internal conflict in the Shimazu family and was finally resolved through intervention by Tokugawa Ieyasu. The rebellion is cited as a reason for the inability of the Shimazu to send a large army to the Battle of Sekigahara.
Course of events
Slaying of Ijūin Tadamune
On 3/9 of Keichō 4 (1599), at the Shimazu residence in Fushimi, Shimazu Tadatsune slayed Ijūin Tadamune with a sword. Tadamune was the head of the chief retainers of Shimazu Yoshihisa, a sengoku daimyō and the sixteenth head of the Shimazu clan. Tadamune was a meritorious retainer of the Shimazu clan supporting the expansion of their power in Kyūshū. During the Subjugation of Kyūshū by Toyotomi Hideyoshi, based on a recognition of the disparity in power between the Toyotomi and Shimazu clans, Tadamune advocated for an early surrender. After surrendering, he became a hostage and went to Kyōto to manage affairs in the aftermath of the war, contributing to the preservation of the Shimazu clan. As a result, he was recognized as a representative retainer of the Shimazu family and was granted the Kimotsuki District in Ōsumi Province directly from Hideyoshi.
In 1594, after a survey of the territory held by the Shimazu, the Ijūin clan was allocated 80,000 koku in Miyakonojō based on a certificate with the seal of Hideyoshi. Miyakonojō was the homeland of the Hongō clan, but owing to the young age of their lord, Hongō Tadayoshi, and insufficient levels of service in the Keichō Campaign, the Hongō were transferred to Kedōin and their fief reduced from 69,000 koku to 37,000 koku. Tadamune received direct orders from Hideyoshi to manage the reallocation of fiefs after the land survey. Consequently, Tadamune became the target of dissatisfaction among members of the clan whereupon he was regarded as a crafty person who caused trouble for the family. Moreover, the residence of the Ijūin clan in Fushimi was more spacious than the residence of the main branch of the Shimazu in Fushimi and, in Satsuma, rumors circulated that the Ijūin sought to overtake the head family of the Shimazu.
Tadatsune was the third son of Shimazu Yoshihiro who, in turn, was the younger brother of Yoshihisa (the head of the Shimazu clan). Yoshihisa did not have any sons, while Tadatsune’s older brother, Shimazu Hisayasu, died early so Tadatsune wed Yoshihisa’s third daughter, Kameju, and became the successor to the main branch of the Shimazu. According to one account, fter the death of Hideyoshi in the eighth month of 1598, Tadatsune returned from Korea and was informed by Ishida Mitsunari or Tokugawa Ieyasu that Ijūin Tadamune had plans to rebel. This account, however, is not substantiated in other records from this period. As the successor to the Shimazu clan, Tadamune recommended Shimazu Teruhisa, the husband of Yoshihisa’s second daughter (and Yoshihisa’s son-in-law). Tadatsune loathed Tadamune. During the Keichō campaign in Korea, adequate provisions were not furnished from the home province to Tadatsune and the expedition army. Tademune did not deploy to Korea and Tadatsune considered Tadamune to be the reason for the inadequate provisions. He was also detested by retainers of the Shimazu and, as a result, when Yoshihisa and Yoshihiro were absent, Tadatsune called Tadamune and then slayed him with a sword.
Although Tadamune was a retainer of the Shimazu clan, he had officially recognized rights to a fief of 80,000 koku in Miyakonojō. From the perspective of the Toyotomi administration, the murder of Tadamune who was treated as a daimyō independent of the Shimazu clan amounted to an act of treason against the administration. Tadatsune expressed penitence at the Jingo Temple on Mount Takao while Tadamune’s wife and children moved to the Tōfuku Temple. At the time, Tokugawa Ieyasu held power and as the ultimate lord could determine that fate of rebellious retainers. Owing to his support for the actions of Tadatsune, Tadatsune was permitted to return to the Shimazu residence in Fushimi.
Meanwhile, Yoshihisa explained to Ishida Mitsunari that the murder of Tadamune was occasioned solely by Tadatsune’s own actions and that he was not involved whatsoever. In an account written in a later era, Yoshihiro and Tadatsune conspired to commit the murder while Yoshihisa gave his consent, and, on 3/3 in the month after the incident, Yoshihisa prohibited retainers from traveling to Miyakonojō and obtained written pledges from them not to ally with Tadazane.
Rebellion by Ijūin Tadazane
When news arrived of Tadamune’s slaying, his lineal heir, Ijūin Tadazane, was on a hunting expedition on Mount Ōkawahara in the environs of Miyakonojō in Ōsumi Province. He then rushed home, and, after consulting with family members and retainers, decided that his uncle, Ijūin Shinemon, plead for recognition of their rights to their former territory but Shiraishi Eisen, a guest commander (and the abbot of the Kōsai Temple and a former monk at the Kishū-Negoro Temple) advocated for resistance to the bitter end. Ultimately, the clan adopted Eisen’s position and committed to rebelling against the head family of the Shimazu.
Meanwhile, in a letter dated 6/18 sent by Tadazane to Kawakami Tadatomo, he noted: “Soon after the death of my father, I went to visit Yoshihisa-sama. I told him that I intended to obey the orders of Yoshihiro-sama and Tadatsune-sama but Yoshihisa-sama was not convinced at all and prohibited me from traveling to Shōnai. It appears that I will be treated similarly to my father and they will set fire around the boundaries of my land.” He asserted that Yoshihisa intended to extinguish the Ijūin clan. Based on this letter, Tadazane requested mediation by Yoshihiro but, instead, Yoshihiro demanded that he surrender.
In Miyakonojō, Miyakono Castle served as the main base, and was protected by twelve auxiliary castles including Tsuneyoshi, Umekita, Shiwachi, Kajiyama, Katsuoka, Yamanokuchi, Gassanhiwa, Yasunaga, Nonomidani, Sueyoshi, Yamada, and Takarabe castles so could not easily be attacked. Tadazane bolstered the defenses at each auxiliary castle and positioned family members and retainers to prepare for an attack. According to military chronicles of Shōnai, he had 20,000 troops but, in fact, he only had 8,000 men. In addition, he received covert shipments of provisions from landlords of territories adjacent to the Shimazu, including Katō Kiyomasa and Itō Suketake. For their support of Tadazane, these neighboring daimyō were the subject of objections by the Shimazu.
Deployment by Shimazu Tadatsune
To suppress the rebellion, Tadatsune received permission from Tokugawa Ieyasu to return to his home province. In the sixth month, he departed from Kagoshima to establish a main base at the Kongō-Bussaku Temple at Higashi-Kirishima and proceeded to attack Shōnai. Members of the Shimazu clan and senior retainers joined in the battle. In particular, the Hongō clan fought valiantly, viewing the potential defeat of Tadazane as a means to recover their original homeland in Miyakonojō. According to records from the town of Takagi, Tadatsune fielded 30,000 to 40,000 troops.
Ieyasu sent a retainer named Yamaguchi Naotomo as a messenger followed by Terazawa Hirotaka (who served as a mediator for the Toyotomi administration in Kyūshū) to promote reconciliation but these efforts were unsuccessful. He further ordeted assorted daimyō in Kyūshū to deploy in support of the Shimazu clan, including Shimazu Toyohisa, Akizuki Tanenaga, Itō Suketake, Sagara Yorifusa, Takahashi Naotsugu, Takahashi Mototane, Ōta Kazuyoshi, Tachibana Muneshige and Konishi Yukinaga but Toyohisa, as a member of the Shimazu clan, had already deployed and the Shimazu clan was not in favor of depending upon other families to subdue their retainers in a rebellion so they firmly rejected their participation. Those who actually sent forces to Shōnai were limited to Akizuki Tanenaga, Takahashi Mototane, and Ōta Kazuyoshi. Upon the outbreak of hostilities, Tadatsune toppled and entered Yamada Castle. Next, he felled Tsuneyoshi Castle, but, thereafter, his progress stalled and the conflict evolved into a stalemate. Thereafter, Tadatsune set-up a base in Morita between Nonomidani and Shiwachi and laid siege to Shiwachi Castle by blocking its provisioning. Tadazane attempted to send food provisions to Shiwachi Castle but failed, leading to desperate circumstances within the castle.
Owing to the contributions of resourceful commanders such as Shiraishi Eisen fighting for Tadazane, Tadatsune’s forces incurred many losses. Yoshihisa himself deployed and led a failed assault against Takarabe Castle in the Koyu District of Hyūga.
Surrender by Ijūin Tadazane
Ieyasu dispatched Yamaguchi Naotomo as his messenger to facilitate a mediation. Naotomo received a statement from Yoshihisa and Tadatsune that if Tadazane surrendered, he would be treated the same as before. Naotomo presented this statement to Tadazane and encouraged him to surrender. According to one scholar, the conflict did not lead to the deployment of forces by neighboring daimyō nor expand beyond an internal matter because the Shimazu accepted mediation under the authority of Ieyasu and, in addition to Yamaguchi Naotomo, deployed Terazawa Hirotaka to mediate in the name of the authorities backed, in part, by the mobilization of forces by neighboring daimyō. Suppression of the rebellion reflected the power of authorities to maintain security across Japan and a rejection of the phenomenon of gekokujō witnessed during the Sengoku period by which persons of lower status usurped those above them. This was consistent with the power to maintain security throughout the provinces earlier evidenced by an edict issued by Toyotomi Hideyoshi in 1585 that banned war between provincial daimyō on the basis of territorial or personal disputes.
Certain researchers have criticized as being one-sided the assertion that Ieyasu intervened in the conflict in Shōnai and leveraged the power of the central authorities to expand his influence which view is based on the traditional theory that he ignored the last wishes of Hideyoshi from the onset.
On 2/6 of Keichō 5 (1600), those defending Shiwachi Castle surrendered. Thereafter, one after another, those at other auxiliary castles surrendered. Tadazane, through mediation by Ieyasu, surrendered on 3/15, whereupon he was moved to Ei in the southern part of Satsuma with a fief of 10,000 koku. Later, he was moved to Chōsa with a fief of 20,000 koku. The Hongō clan recovered their ancestral homeland of Miyakonojō and the rebellion came to an end. It is noted that Mōri Terumoto also took various steps in an effort to resolve the conflict.
The following year, in 1601, Yoshihisa, Yoshihiro, and Tadatsune jointly issued official orders prohibiting members of the Shimazu clan from engaging with the Ikkō sect. This was a cause of the secretive practice of the religion which was the subject of suppression by the authorities. There is a theory that this policy was related to the fact that Tadamune had been an ardent follower of the Ikkō sect.
Decimation of the Ijūin clan
In the wake of the rebellion, Tadatsune remained vigilant of Tadazane. In fact, Tadazane sent a secret messenger to Katō Kiyomasa of Higo Province to appeal for his support to exact revenge against the Shimazu. The secret letter, however, that Tadazane entrusted to Ijūin Jinkichi was instead turned-over to Tadatsune. This enraged not only Tadatsune but also Tokugawa Ieyasu who would not permit Tadazane to stand as an enemy of the Shimazu. Meanwhile, owing to his communications with Tadazane, Kiyomasa also became the target of Ieyasu’s anger who prohibited Kiyomasa from traveling to the capital and ordered him to remain confined to his home province. Further, Ieyasu did not permit Kiyomasa to serve in the Conquest of Aizu. As a result, during the Battle of Sekigahara, Kiyomasa engaged in fighting in Kyūshū far away from the main battlefield.
On 8/17 of Keichō 7 (1602), when Tadatsune planned to visit the capital, he ordered Tadazane to accompany him, and, while hunting in Nojiri in Hyūga, shot him to death. At the time, Tadazane had exchanged horses with another retainer of the Shimazu named Hirata Munetsugu and this horse also died in the incident. Externally, the murder of Tadazane was characterized as an accident and those who committed the act, namely, Oshikawa Noriyoshi and Fuchiwaki Hirauma were ordered to commit seppuku, but, in fact, it was a premeditated killing. On the same day, Tadazane’s mother and three younger brothers were also killed. There is a theory that the death of Hirata Hirauma, whose father, Hirata Masumune, a chief retainer of the Shimazu who previously backed Shimazu Hisanobu as the successor to the Shimazu family, was an element of the same plot. Tadazane was a leading figure in the faction supporting Hisanobu.