Battle of Yasumimatsu
Year: Eiroku 10: 1567 (9/3)
Location: Near Yasumimatsu Castle in Chikuzen Province in northern Kyūshū
Outcome: The Ōtomo clan prevailed in the initial stages of the conflict; a surprise attack at nighttime by the Akizuki resulted in a significant loss for the Ōtomo.
The Battle of Yasumimatsu occurred on 9/3 of 1567 in Chikuzen Province between the Akizuki and Ōtomo clans.
The original name of the Akizuki was Ōkura, distinguished through the ties of descendants to the Chinese emperor. From the Kamakura period, the Yasu District in Chikuzen served as the base of the Akizuki, where the clan maintained a proud lineage along with the local Harada and Takahashi clans. Akizuki Fumitane served as the fifteenth head of the Akizuki clan and lord of Koshosan Castle in Chikuzen.
In 1557, Fumitane and his eldest son and lineal heir, Akizuki Harutane, killed themselves after suffering a fierce attack by Ōtomo Yoshishige at Koshosan. Fumitane’s second son, Akizuki Tanezane, was taken by his retainers and escaped Koshosan Castle just before it fell. He landed in Yamaguchi in Suō Province under the protection of the Mōri clan. In 1559, a former retainer of the Akizuki named Fukae Mino-no-kami received support from the Mōri to join with Tanezane to defeat the Ōtomo and recapture Koshosan Castle. This enabled Tanezane to recover the clan’s home base and most of their former domain.
After returning to Koshosan, Tanezane endeavored to expand his influence, making clear his opposition to the rival Ōtomo. Meanwhile, the Ōtomo viewed the return of Tanezane as a threat to their dominion. Tanezane conspired with Takahashi Akitane to conduct a rebellion against the Ōtomo. On 8/14 of 1567, experienced commanders including Bekki Akitsura (later known as Tachibana Dōsetsu), Yoshihiro Akimasa, and Usuki Akisumi led a contingent of 20,000 soldiers into the Akizuki territory. The initial clash on 8/14 between the Ōtomo army and the Akizuki is known as the Battle of Amouzu-Haseyama (or the Battle of Uryūno) with an attack on 8/15 against the auxiliary site of Yū Castle. The Ōtomo forces proceeded to attack Yasumatsu Castle defended by Sakata Moromasa. A ferocious assault overwhelmed the defenders while Moromasa took his own life. Having deployed nearby, Bekki Akitsura devised a plan of attack against Koshosan Castle, but the castle was staunchly defended. As the conflict headed toward a deadlock, Akitsura learned of signs that the Mōri from the western region of Japan were planning an invasion of Kyūshū. This caused trepidation among the kokujinshū, or local clans of influence under the governance of the Ōtomo, in Buzen, Chikuzen, and Chikugo provinces, causing them to abandon their landholdings. Owing to these circumstances, Ōtomo Yoshishige, the head of the Ōtomo clan, directed the forces to retreat.
Pursuant to orders, on the morning of 9/3, the Ōtomo forces decamped and began to withdraw from the area near Koshosan Castle. Upon hearing of these plans, Tanezane divided 12,000 mounted soldiers under his command into a hornbeam attack pattern, with Monjūjo Munekage and Uchida Sanehisa each leading 3,000 men, and Ayabe Suruga-no-kami commanding 5,000 men. Scouting the movements allowed Akitsura advance notice of the impending attack, whereupon he dispatched 3,000 soldiers to the area of Yoshimitsu to lay in wait. The spirited counterattack was led by 500 mounted soldiers under Ono Shigeyuki and Yufu Korenobu, together with another 600 men under Akitsura. Munekage attempted an attack with 2,000 men against Akitsura’s main contingent, killing Totoki Koretada, a commander for the Bekki, with a firearm. Nevertheless, Uchida Shigeie and Hori Aki-no-kami led 600 men with battle flags in the air to serve as reinforcements from the rear guard. The assault rattled Munekage’s forces, imposing many casualties and compelling a withdrawal. Meanwhile, Akitsura prepared for a possible nighttime attack by Tanezane, ordering his troops not to remove their armor, keeping the horses saddled, and arms at the ready.
Nighttime attack by Tanezane
As the wind and rain poured at midnight on 9/4, Tanezane committed to lead 2,000 soldiers on a surprise attack against the camp of Usuki Akisumi and Yoshihiro Akimasa. Having failed to anticipate the attack, the Ōtomo army quickly fell into disarray, with soldiers witnessing their comrades fall in the raid. Akitsura quickly responded to support the Usuki and Yoshihiro forces and ordered a withdrawal. Owing to Akitsura’s strenuous efforts, the army managed to withdraw, but the disastrous clash resulted in the death of over 400 soldiers and commanders from the Ōtomo army. The Akizuki forces continued to pursue the Ōtomo army to Yamaguma Castle in Chikugo Province, with the Ōtomo incurring further casualties in retreat.