# Oyama Castle

- **Country:** Japan
- **Location Text:** Haibara District, Shizuoka

Oyama Castle, also known as Gion Castle, was a historic Japanese fortress located in the city of Oyama within Tochigi Prefecture. Constructed in 1148 by Oyama Masamitsu, the structure was designed in the hirayama style, utilizing the flatlands alongside the Shikawa River which served as a massive natural moat. The complex originally featured three large enclosures arranged in a row along the water, separated by deep artificial moats and earthworks. For centuries, it served as the primary seat of the powerful Oyama clan, who claimed descent from Fujiwara Hidesato and held significant influence as shugo governors during the Kamakura period before relocating here from the nearby Washi Castle for better defense.

The castle played a pivotal role in regional military history, witnessing numerous conflicts between 1380 and 1383 as the Oyama clan fought against rival families like the Utsunomiya and Kō clans. Although the main clan was eventually annihilated, the site remained strategically vital. In the late sixteenth century, it was expanded by Hōjō Ujiteru to support the Late Hōjō clan's conquest of northern Kantō. Following the defeat of the Hōjō by Toyotomi Hideyoshi in 1590, the fortress was granted to Honda Masazumi as the center of a 30,000 koku fief under the Tokugawa Shogunate. However, when Honda was transferred to Utsunomiya Castle in 1619, Oyama Castle was abandoned and subsequently demolished.

Today, the site exists only as ruins but holds significant cultural value, having been collectively designated a National Historic Site of Japan in 1991 alongside the ruins of Nakakuki and Washi Castles. During the Meiji period, a villa was built on the grounds by politician Hoshi Tōru, though this structure no longer stands. The area has since been transformed into Shiroyama Park, which is open to the public. Visitors can explore the remnants of the earthworks and moats that once defined this important military installation, preserving the memory of the Oyama clan's legacy in the Kantō region.

![Photo of Oyama Castle](https://upload.wikimedia.org/wikipedia/commons/2/22/Oyam-jo.entrance.2.JPG)

**Source:** https://en.wikipedia.org/wiki/Oyama_Castle (Wikipedia, CC BY-SA)