The Battle of Koromo River took place during the opening years of the Kamakura period

Kamakura period

The is a period of Japanese history that marks the governance by the Kamakura Shogunate, officially established in 1192 in Kamakura by the first shogun Minamoto no Yoritomo....

 (12th century) of Japan.

After the destruction of Heike

Heike

Heike may refer to:* Heike clan, a Japanese clan name* Heikegani, a species of crab named after the Heike clan* Heike * The Tale of the Heike, an epic account of the struggle between the Taira and Minamoto clans for control of Japan at the end of the 12th century in the Genpei War...

, Minamoto no Yoshitsune

Minamoto no Yoshitsune

was a general of the Minamoto clan of Japan in the late Heian and early Kamakura period. Yoshitsune was the ninth son of Minamoto no Yoshitomo, and the third and final son and child that Yoshitomo would father with Tokiwa Gozen. Yoshitsune's older brother Minamoto no Yoritomo founded the Kamakura...

 conflicted with his brother Minamoto no Yoritomo

Minamoto no Yoritomo

was the founder and the first shogun of the Kamakura Shogunate of Japan. He ruled from 1192 until 1199.-Early life and exile :Yoritomo was the third son of Minamoto no Yoshitomo, heir of the Minamoto clan, and his official wife, a daughter of Fujiwara no Suenori, who was a member of the...

, and fled into Hiraizumi

Hiraizumi, Iwate

is a town located in Nishiiwai District, Iwate, Japan. It was the home of the Hiraizumi Fujiwaras for about 100 years in the late Heian era and most of the following Kamakura period. At the same time it served as the de facto capital of Oshu, an area containing nearly a third of the Japanese land...

, Mutsu Province

Mutsu Province

was an old province of Japan in the area of Fukushima, Miyagi, Iwate and Aomori prefecture and the municipalities of Kazuno and Kosaka in Akita Prefecture...

. He was sheltered by Northern Fujiwara

Northern Fujiwara

The Northern Fujiwara were a Japanese noble family that ruled the Tōhoku region of Japan from the 12th to the 13th centuries as if it were their own realm. They succeeded the semi-independent Emishi families of the 11th century who were gradually brought down by the Minamoto clan loyal to the...

's 3rd ruler Fujiwara no Hidehira

Fujiwara no Hidehira

was the third ruler of Northern Fujiwara in Mutsu Province, Japan, the grandson of Fujiwara no Kiyohira. During the Genpei War, he controlled his territory independently of the central government; however, he was the official imperial governor for Mutsu Province as of 1181. He offered shelter to...

. Hidehira appointed Yoshitsune as general to be opposed to Yoritomo, but he died of illness on October 29, 1187.

Yoritomo strongly pressured Fujiwara no Yasuhira

Fujiwara no Yasuhira

was the fourth ruler of Northern Fujiwara in Mutsu Province, Japan, the second son of Hidehira. Against his father's will, he first hid Yoshitsune in escape but later killed him, fearing the possibility of Yoritomo's intervention...

, the 2nd son and successor of Hidehira, through the Imperial Court to arrest Yoshitsune. Against the will of his father, Yasuhira succumbed to the repeated pressure of Yoritomo. June 15, 1189, he attacked ten-odd Yoshitsune and servants by 500 soldiers in the Koromogawa no tachi residence. Yasuhira defeated Yoshitsune and his compatriot, Saitō no Musashibō Benkei. Throughout the battle, Benkei defended his lord. Benkei supposedly died standing up, which caused great fear in his enemies. Yoshitsune himself committed suicide at the end of the battle.