Siege of Iwasaki Castle
Location: Iwasaki Castle in the Yamada District of Owari Province
Outcome: Niwa Ujitsugu, the lord of Iwasaki Castle, assigned his younger brother, Ujishige, to defend the castle while Ujitsugu was absent to participate in the Battle of Komaki-Nagakute. Soon thereafter, Ikeda Tsuneoki and Mori Nagayoshi led respective divisions to attack and topple Iwasaki Castle in the course of one day, leaving Ujishige and many other defenders killed in action.
The Siege of Iwasaki Castle occurred in 1584 and was waged between Niwa Ujishige (on behalf of Tokugawa Ieyasu) and Ikeda Tsuneoki (on behalf of Hashiba Hideyoshi). Iwasaki Castle was on a hilltop surrounded by plains in the Yamada of Owari Province. When this battle erupted, Niwa Ujitsugu (the lord of Iwasaki Castle) was on deployment in Komaki to fight under Tokugawa Ieyasu, while his younger brother, Niwa Ujisuke, remained behind to defend the castle.
Course of events
The vanguard forces from Mikawa that traversed the Kanare River in Yazako included the First Division of 7,000 soldiers under the command of Ikeda Tsuneoki and Ikeda Motosuke (father and son) and the Third Division of 5,000 soldiers under Hori Hidemasa. These divisions advanced to 生牛ヶ原 and 金荻原. A detachment from the Second Division of 3,000 soldiers under Mori Nagayoshi was sent to burn down Isshiki and Nagakute castles.
Niwa Ujishige (who observed the flames while protecting Iwasaki Castle on behalf of his brother, Niwa Ujitsugu) and Katō Kagetsune (the lord of Nagakute Castle) dispatched scouts who confirmed the advance of the opposing forces without torches, whereupon they summoned their troops to prepare for battle and relocated the women and children from a dry moat to the northwest to the Myōsen Temple. The defenders then launched a preemptive attack at 4:00 AM. The Ikeda forces counterattacked while the defenders from Iwasaki Castle withdrew. In the wake of this attack, orders were given for the Ikeda forces to surround Iwasaki Castle. At 5:00 AM, Igi Tadatsugu led 2,000 soldiers in an attack on the main gate while Katagiri Toshitada attacked the rear gate with another 2,000 men.
Ujishige responded by charging out of the main gate, repelling the attacking forces three times. During these counterattacks, some of the attacking forces sustained injuries falling into the moat. At the height of the battle on the stone bridge outside the castle, Ujishige faltered and was killed after warning shots were fired from Takenoyama by arquebusiers in the division led by Mori Nagayoshi who had come south from Gifune.
The castle defenders focused on the Ikeda forces but Nagayoshi broke-through a lightly defended opening in the northwest portion of the castle grounds. A portion of the defenders scattered and hid to protect themselves but the scene turned into mayhem and the castle fell around 7:00 AM. Younger brothers of Ujishige including Denshichirō and Shirōemon also died in action.
Niwa Shigetsugu (the younger brother of Niwa Shigenobu who inherited the role of chief retainer from Niwa Shigemasa) headed toward the Komakiyama fortress to convey an urgent message of the enemy assault on Iwasaki Castle, but he arrived after Ujitsugu and the Tokugawa army had departed. On his return, when he encountered Ujitsugu in the foothills of Hatakegane, Iwasaki Castle had already fallen, his brethren engaged in backbiting, so three months later, at the Battle of Kanie in the Ama District, he sought to overcome his shame by taking the lead and dying in battle.
Exhausted from battle, the soldiers in the Ikeda division gathered on Mount Rokubō to have breakfast, rest, and count the heads of enemy combatants. The commanders then began a proceeding to confer honors upon men under their command who made contributions on the battlefield. Members of the Hori division brought provisions and provided meals but soon departed following a request from Hashiba Nobuyoshi for reinforcements. As a result, orders were given to return to battle at 8:00 AM. The Mori division quickly returned to Mount Rokubō and then withdrew to Gifune, set-up a camp, and awaited the arrival of the Ikeda division.
After Niwa Ujitsugu (the lord of Iwasaki Castle) received the report from Niwa Shigetsugu in the foothills of Hatakegane, he dispatched a unit of twenty reinforcements led by his chief retainer, Suzuki Mitsusumi, and Mitsusumi’s son, Shigemasu, to head toward Iwasaki Castle. Ujitsugu himself remained for the uphill attack on Hatakegane. The reinforcements confirmed that the Ikeda division had abandoned 238 heads of castle defenders midway up Mount Rokubō and then converged with Ujitsugu’s forces. Only the head of Niwa Ujishige, the castle chamberlain, had been taken to Nagakute. Haruta Masayoshi observed soldiers from the Ikeda division carrying the head of Ujishige near Hotokegane, whereupon he pursued them and returned the head to Tokugawa Ieyasu for which he was praised.