Date: Winter of Tenshō 2 to fifth month of Tenshō 3 (1574 to 1575)
Location: Bitchū-Matsuyama Castle and surrounding castles controlled by the Mimura clan in Bitchū Province
Outcome: Mimura Motochika, lord of Bitchū-Matsuyama Castle, lost to the Mōri army who first toppled the surrounding castles and then laid siege to Bitchū-Matsuyama until the defenders capitulated.
The Bitchū Conflict occurred from the winter of Tenshō 2 to the fifth month of Tenshō 3 (1574 to 1575) in Bitchū Province. In this conflict, Mimura Motochika, a sengoku daimyo in Bitchū, sought to defend his castle against a combination of the Mōri army and reinforcements from the Ukita clan. Bitchū-Matsuyama Castle was an impregnable fortress, so the Mōri deployed a strategy to first topple all of the surrounding castles held by the Mimura, and then lay siege to Bitchū-Matsuyama until the defenders lost their will to fight.
Prelude to the battle
During the first half of the Sengoku period, Bitchū was occupied by an assortment of small landowners. Powerful daimyō including the Ōuchi from Suō and the Amago from Izumo each sought the support of these landowners in their competition for regional hegemony.
In 1533, Shō Tamesuke, the lord of Sarukake Castle, joined forces with the Amago clan to defeat Ueno Yoriuji, the owner of land around Bitchū-Matsuyama Castle, and then established a base in this location. Meanwhile, the Mimura clan based in Kakushu Castle who governed the area from Hoshida to Nariwa also sought to control Bitchū. The Mimura allied themselves with the Amago clan in opposition to the Mōri. In the era of Mimura Iechika, the Mimura expelled the Shō clan, moved to Bitchū-Matsuyama Castle, and garnered control of almost all of Bitchū and a portion of Bizen Province.
However, in 1566, Iechika was assassinated by Ukita Naoie, a retainer of Uragami Munekage of Bizen. In 1567, his son and heir, Mimura Motochika, led an army of about 20,000 soldiers to avenge the loss of his father by invading Bizen in the Battle of Myōzen Temple. Naoie deployed clever tactics to draw-out Motochika and the Mimura army suffered a major defeat at the hands of an Ukita army of 5,000 men.
In 1568, Naoie invaded Bitchū, taking advantage of the participation by forces from Bitchū under the command of the Mimura in the Invasion of Kyūshū by the Mōri. On this occasion, Shō Takasuke of Bitchū-Matsuyama Castle and Ueki Hidenaga of Saida Castle switched their allegiance to the Ukita clan. The Ukita forces used this as an opportunity to attack and topple Sarukake Castle. Out of concern of this developments, Mōri Motonari of Aki Province dispatched his fourth son, Mōri Motokiyo (later known as Hoida Motokiyo), to recapture Sarukake and, further, to attack Bitchū-Matsuyama Castle, expelling the Shō clan. After finally recapturing Bitchū-Matsuyama, Motochika invested significant resources to harden the defenses of the castle.
Details of the battle
In 1574, the Mōri clan entered into an alliance with Ukita Naoie through the offices of Motonari’s third son, Kobayakawa Takakage, who governed the Sanyō region. This occurred over the opposition of Motonari’s third son, Kikkawa Motoharu, governor of the Sanin region, who viewed Naoie as a duplicitous character, disrespectful of the Mimura clan and without honor. As a result, Motochika, who harbored enmity toward the Ukita, separated from the Mōri and colluded with Oda Nobunaga. His uncle, Mimura Chikanari and uncle’s son, Mimura Chikanobu, disagreed with Motochika’s actions so decided to cut ties with him and flee. In the winter of 1574, Mōri Terumoto responded to the estrangement of the Mimura by dispatching Kobayakawa Takakage to lead a contingent of 80,000 soldiers into Bitchū, triggering the Bitchū Conflict. Meanwhile, Motoharu asserted that the army should avoid a campaign to eliminate the Mimura and proposed that he should meet with Motochika to persuade him to change course. Failing to convince the others, he lamented that, without honor, the future of the Mōri family would be dark. Several years later, the concerns expressed by Motoharu became true after Naoie switched his allegiance to the Oda.
Bitchū-Matsuyama Castle, which served as the base for the Mimura army, was reinforced with twenty-one towers projecting from the main castle. Consequently, the Mōri army began by toppling the surrounding castles, including Sarukake, Saida, Kuniyoshi, and Kakushu. Once Bitchū-Matsuyama Castle stood alone, rather than attempt to capture it by force, the commanders opted for a battle of attrition by blocking the provisioning of the castle so that it would eventually collapse from within. Almost one month after the castle had been surrounded, the morale of the Mimura troops inside the castle began to wane. After the loss of the tallest tower as a result of collusion, other defenders followed suit. Bitchū-Matsuyama fell in the fifth month of 1575. Initially, Motochika’s retainers convinced him to escape along with his wife and children, but then, having resolved himself to commit seppuku, made this request to Kobayakawa Takakage. After Takakage’s acknowledged the request, Motochika left a farewell message addressed to his elderly mother from the Awa-Miyoshi clan and a close associate named Hosokawa Fujitaka and then took his own life in the Shōren Temple on the grounds of Bitchū-Matsuyama.
After the fall of Bitchū-Matsuyama, the Mōri proceeded to sweep-up all of the castles associated with the Mimura to pacify the province. Ueno Takanori, the husband of Motochika’s younger sister, Tsuruhime, resided in the last castle controlled by the Mimura, known as Tsuneyama Castle. Together with Tsuruhime and other occupants, Takanori led a valiant fight against the Mōri, but the outnumbered defenders lost the castle, marking the final chapter of the Bitchū Conflict. Prior to these events, on 1/8 of 1575, the Mōri army attacked Mimura Motonori, lord of Yuzuri Castle, and captured it. On 1/7, Kawanishi Saburō-Emon Yukihide, lord of Arahirayama Castle, was exiled to Sanuki Province in Shikoku in exchange for having spared the lives of his men.
The Bitchū Conflict resulted in the elimination of the Mimura clan as sengoku daimyō in the province. Motochika’s uncle, Chikanari, obtained recognition to retain landholdings, albeit to a smaller scale owing to his inability to dissuade Motochika from opposing the Mōri, for which he was scorned. Chikanari was also allowed to continue his role as the lord of Kakushu Castle in Nariwa. Chikanari took care of Motochika’s younger sister as his niece and others from the main branch of the Mimura family. Subsequent generations of the family continued into the Edo period, serving as elders of the Mizuno clan for the Bingo-Fukuyama domain with a fief of 1,500 koku.
Thereafter, the majority of Bitchū came under the control of the Mōri while the Ukita were granted a southern part of the province.