Yokoyama Party (横山党)
The Yokoyama Party, centered in the Yokoyama-sho estate in Tama County, Musashi Province (the present Hachioji City, Tokyo), was an armed group from the same family that existed from the late Heian period to the Kamakura period, and based themselves in Musashi Province (Osato County, Hiki County, and Tachibana County) and the northern part of Sagami Province. It was one of the Musashi-shichito Parties (seven parties of samurai in Musashi Province). Ienaga CHUJO, who was involved in the establishment of code of conduct for samurai as the first member of the Council of State, and Suetaka AIKO, who was a very skillful archer and slew Shigetada HATAKEYAMA, were well known as members of the Party. The party fell at the Battle of WADA. Inomata Party was also in this family.
Place of origin
It is generally believed that the party were descendants of ONO no Takamura; however, Motohisa YASUDA carefully examined family trees, and calculated the number of years among generations, and studied appointments of kokushi (provincial governors) at that time, and consequently thought that this was contrived by later generations, and the party were actually descendants of kaihatsu-ryoshu (local notables who actually developed the land), and passively supported a view that the party may have been descendants of Musashinokuni-no-MIYATSUKO, which is a view found in the "Seishi Kakei Jiten" (Dictionary of Family Names and Lineages in Japan) by Akira OTA.
It is believed that the party was based in Yokoyama, Tama County, Musashi Province (the present Moto-Yokoyama Town, Hachioji City, Tokyo) and gave themselves the family name of Yokoyama.
At that time, 'yokoyama' referred to the Tama Hills and in "Manyoshu" (the oldest anthology of Japanese poetry) the hills are called 'yokoyama in Tama.'
Heian period
In 924, when the Ono clan arrived to take up Musashi no kami (Governor of Musashi Province), the clan erected Hachimanyakumo-jinja Shrine to transfer a divided tutelary deity of Iwashimizu Hachiman-gu Shrine to a new location.
In 1113, because of the murder of Naiki Taro AIKO, the members of the party were searched out and destroyed. The party was subject to MINAMOTO no Tameyoshi.
During the Hogen War in 1156, and the Heiji War in 1159, the party followed the troops under MINAMOTO no Tameyoshi's command (some say that the party was subordinate to the Hatakeyama clan) and they fought bravely.
Kamakura period
According to "Heike Monogatari" (The tale of the Heike), the party also took an active part in the Jisho-Juei Civil War.
When MINAMOTO no Yoritomo established Kamakura bakufu (Japanese feudal government headed by a shogun), as a reward for military service Tokihiro YOKOYAMA from the Yokoyama Party received a fief and was approved as the landowner of the Yokoyama-sho estate.
At the Battle of WADA in 1213 Tokikane YOKOYAMA and his party reinforced Yoshimori WADA, and suffered a crushing defeat in Kamakura.
Yokoyama-sho estate, which was the base of the Yokoyama Party, was given to OE no Hiromoto. In 1214, OE no Hiromoto founded Yokoyama-jinja Shrine to enshrine Yoshitaka YOKOYAMA, the founder of the Yokoyama Party, in the precincts of Hachimanyakumo-jinja Shrine.
Motohisa YASUDA assumes that with its many branch families the Yokoyama Party would have been proud of its power and influence.