In 1584, Date Terumune turned control of the clan over to his son Masamune. Later in 1585, Date was betrayed by his vassal Ouchi Sadatsuna, so Masamune began a campaign of annihilation of his household. In August 1585, Masamune laid siege to Sadatsuna's fortress off Otemori-no quarter was given.

The conquest of Otemori heated tensions between lord Hatakeyama and Masamune. Hatakeyama requested peace talks but Masamune would always reject. Finally he approached Terumune and asked for his assistance. On 7 October, Masamune and Hatakeyama finally met in person; both shared a wonderful feast together and talked about their further alliance.

The next day Hatakeyama went to visit Terumune and express his gratitude, however, he kidnapped Terumune at knife point and rode off with him. Masamune, who was out practicing falconry, immediately went in pursuit when he returned and found his father missing. He caught up with them near the Abukuma River, which bordered Hatakeyama's province. Terumune cried out for them to "shoot us, do not hesitate," but Masamune would not fire for fear of hitting his father. Finally, Hatakeyama was surrounded, and knowing he was doomed, killed Terumune. Masamune instantly retaliated, putting him and his followers to the sword.

All out war was soon waging between the two families. Hatakeyama son, Kunioh-maru, soon received aid from Satake, Ashina, Iwaki, Ishikawa, Nikaido, Soma and Shirakawa. They gathered together at the River Suka and headed north to defeat Masamune. By 16 November they were in the field just south of Masamune's castle at Maedazawa. When Masamune heard about this he gathered his forces, but he was at a distinct numerical disadvantage as he only had 7,000 men to use against 30,000 of the enemy.

Motomiya was a key castle of Date's and its fall would signal the downfall of the clan. It was defended by a network of fortresses, Takakura, Tamanoi, Maedazawa, and Setogawa Mansion. The nearby Seto River, with its strong current, made a good defensive obstacle.

Masamune prepared his defenses placing Shiroishi Munezane in Tamanoi Castle; Takakura Oumi, Ito Shigenobu, Koori Munenaga, and Tomizuka Oumi in Takakura Castle; Senoe Kageyasu, Nakajima Sokyu, Sakurada Motochika, and Hamada Kagetaka in Motomiya Castle. Masamune's uncle, Shigezane, was positioned in Nukasawa field. Izumita and Nanamiya took up position just south of Hitodori Bridge. Masamune, Watari Motomune, Moniwa Yoshinao, Rusu Masakage, Kokubun Masashige, Harada Munetoki, and Katakura Kagetsuna remained near Kannondoyama with the main body of 4,000.

On the morning of the 17^th Masamune advanced his main force and repositioned Shigezane in Setogawa Mansion, and Munezane, Izu, and Iki Takano near the town of Arai and the Gohyaku River. Meanwhile, the allies began moving to attack Date. On the right moving towards Takakura Castle were Shirakawa Yoshichika, Ishikawa Akimitsu, Nikaido, and Iwaki Tsunetaka. In the middle and heading towards Arai were Ashina Kamewakamaru and Soma Yoshitani. In the rear, traveling up the Aizu Road was the main body of Satake Yoshishige along with Kunioh.

Luck was certainly not on the side of Date that day; Aizu and Takakura Castle were overrun and Nanamiya and Izumita were forced to retreat back to the main body. The Date forces moved to intercept the allies at Hitodori Bridge but they were pushed back by the sheer mass of enemy troops. At Setogawa Mansion, Shigezane just managed to escape capture as the defenses were breached. Moniwa Yoshinao was slain by Kobata in a duel. With the Date now in full retreat, and victory certain, the allies pressed across the Seto River and moved towards Motomiya.

The allies planned to renew the battle the next morning, however, Satake received news that during his absence Satomi Yoshinori had invaded his lands, so Yoshishige was forced to abandon the allies and head back to defend his territory, taking the bulk of the allied army with him. with little strength left to take Motomiya the allies withdrew. Masamune had avoided his Armageddon.