Stories of the Japanese 00549 [Early Kamakura Period] The Oshu Campaign: The End of Yasuhira

The advance of Yoritomo's army was unstoppable. They were finally approaching Hiraizumi, the stronghold of the Oshu Fujiwara clan.
Regarding the capture of Hiraizumi, Yoritomo said,
"We should not rush there with only a thousand or two thousand soldiers. Let us proceed slowly with twenty thousand cavalry. The enemy is already clearly defeated."
He spoke with a sense of composure.
On August 21, 1189 (the 5th year of Bunji), when Yoritomo's army reached Tsukuge Bridge (Kurihara City, Miyagi Prefecture), his attendant Kajiwara Kagetaka composed a poem:
"The forces of Michinoku have joined our side; I shall cross the Tsukuge Bridge and hang Yasuhira's head."
This pleased Yoritomo. He used a pun on "Tsukuge Bridge" to imply that "most of the Michinoku forces have already sided with the Lord of Kamakura."
Kajiwara Kagetaka is the same person who, when he accepted an official post without permission, was subjected to a barrage of insults from a furious Yoritomo, who said things like, "You look sickly, and I always thought you were a fool." However, it seems he had already been forgiven and was serving by Yoritomo's side. He certainly seems skilled at flattering his superiors.
On August 22, Yoritomo's army finally reached Hiraizumi, but Yasuhira's mansion had already been set on fire, and Yasuhira had fled to the north. In the end, Yasuhira left all the fighting to his brothers and retainers, fleeing without ever directly confronting Yoritomo's army.
On August 26, a letter from Yasuhira was thrown before Yoritomo. It read as follows:
"Yoshitsune was protected by my father, Hidehira, and I know nothing of the matter. After my father passed away, I followed your orders and killed Yoshitsune. Should this not be considered a meritorious deed? Why, then, am I being attacked now without cause? Because of this, I have left the lands of my ancestors and am wandering through mountains and forests, suffering greatly. Please forgive me and allow me to join your retainers. If not, please spare my life and send me into exile."
It was a message of total surrender, but Yoritomo completely ignored it. It was the kind of letter Yoritomo would likely despise, and it seemed very unlikely to earn him a pardon.
Hoping to flee as far as Ezo (Hokkaido), Yasuhira had initially escaped to the home of Kawada no Jiro (?-1189) at Niesaku in Hinaigun (Odate City, Akita Prefecture). Kawada no Jiro was a long-time retainer of the Oshu Fujiwara clan.
However, on September 3, Kawada no Jiro betrayed and killed Yasuhira, and on September 6, he arrived to surrender to Yoritomo, bringing Yasuhira's head with him.
You already know how Yoritomo treated this Kawada no Jiro.