Oyama Castle

The castle is also known as Gion Castle (祇園城, Gion-jō) Oyama Castle was built by Oyama Masamitsu in 1148. The Oyama clan claimed descent from Fujiwara Hidesato and had territories in Musashi Province. During the Kamakura period, they held Yūki Castle in Shimōsa Province and were named shugo of Shimotsuke Province under the Kamakura shogunate. However, after the fall of the Kamakura shogunate, their position as shugo was challenged by the Utsunomiya clan, the Kō clan and the Kantō kanreiUesugi clan. Initially, the Oyama clan used Washi Castle as their seat, but relocated to the more defensible Oyama Castle during the time of Oyama Yoshimasa. It was the site of numerous conflicts from 1380 to 1383. The Oyama clan was eventually defeated and annihilated by the Kamakura-fu, but the clan name was permitted to continue as a cadet branch of the Yūki clan into the Sengoku period. Oyama Hidetsuna was forced to pledge fealty to the Late Hōjō clan in 1576, and the castle was expanded by Hōjō Ujiteru and became a base of operations for the Hōjō conquest of the northern Kantō region.