* Image is for illustrative purposes only.Oyama Castle (Tōtōmi Oyama)
小山城（遠江小山城）
Oyama Castle (Tōtōmi Oyama) is a historic castle in Chūbu dating from the Built circa 1558–1570 (Eiroku era); reconstructed by the Takeda in the 1570s, whose lord was Imagawa clan / Takeda Katsuyori (reconstruction).
Overview
Takeda and Tokugawa Front Line
Oyama Castle (Tōtōmi Oyama Castle) is a hill castle located in Yoshida Town, Haibara County, Shizuoka Prefecture, and served as the front-line stronghold where the Takeda and Tokugawa clans fought fiercely over control of Tōtōmi Province (western Shizuoka) during the late Sengoku period. The castle was built on a low mountain near the western bank of the Ōi River and was renovated and fortified by Takeda Shingen and his son Katsuyori as a base for their advance into Tōtōmi. It is renowned for its characteristic crescent moat (mikazuki-bori), a distinctive feature of Takeda-style castle architecture, and is highly regarded by castle researchers as a masterpiece exemplifying the essence of Takeda military engineering.
A Masterpiece of Takeda-Style Castle Architecture
The layout of Oyama Castle consists of the combination of the "maru-umadashi" (semicircular barbican) and "mikazuki-bori" (crescent moat), techniques that the Takeda clan excelled at. This method involved constructing a semicircular barbican as an outpost for sorties from outside the castle and surrounding its front with a bow-shaped moat, creating a sophisticated defensive technique that impeded the invader's advance in complex ways. The mikazuki-bori at Oyama Castle is known as one of the best-preserved crescent moats among Japanese castles and has been designated a Yoshida Town Historic Site as a structure that passes down the Takeda family's castle-building techniques to the present day.
The Takeda-Tokugawa Struggle for Tōtōmi and Oyama Castle
In Genki 3 (1572), Takeda Shingen launched a major western advance campaign (Saijō Campaign) aimed at conquering Tōtōmi and Mikawa provinces and advancing on Kyoto. In this campaign, Shingen decisively defeated Tokugawa Ieyasu at the Battle of Mikatahagara (1572), but died in his war camp the following year in Tenshō 1 (1573). Takeda Katsuyori subsequently continued the offensive in Tōtōmi and Mikawa, with Oyama Castle serving as a key stronghold. After the Takeda forces suffered a major defeat at the Battle of Nagashino in Tenshō 3 (1575), the counter-offensive by the Tokugawa and Oda intensified, and with the fall of the Takeda clan in Tenshō 10 (1582), Oyama Castle ultimately came under Tokugawa control.
Mock Donjon and Restoration
The castle site today features a mock donjon constructed in Shōwa 62 (1987), with exhibits inside introducing Takeda-style castle architecture and the Sengoku history of Tōtōmi. The entire castle site has been developed as Nōmanji-yama Park, with the remains of the mikazuki-bori and maru-umadashi preserved and opened to the public in excellent condition. The ruins around the main citadel in particular have become a celebrated destination attracting many castle enthusiasts as a textbook example of Takeda-style castle architecture, and serve as an essential site for learning about "Takeda castles."
Connection to Swords
## Swords of the Takeda War Machine Oyama Castle functioned as the Takeda clan's outpost for expansion into Tōtōmi Province, so elite units of the Takeda war machine garrisoned there, and the swords they carried were high-quality practical combat blades crafted by swordsmiths of Kōshū (Yamanashi). The Takeda were famous as a mounted cavalry force, and the elite known as the umamawari-shū (mounted retainers) used swords that prioritized cutting power and durability, characterized by the robust construction favored by Kai Province swordsmiths. In the era when the Takeda forces expanded into Tōtōmi and Mikawa, the area around Oyama Castle became a front line where Takeda swords and those of the Tokugawa and Tōtōmi clans faced each other in actual combat. ## Kai Province Swordsmiths and Tōtōmi Swords In Kai Province (Yamanashi), the Takeda's home base, swordsmiths were also active and are said to have crafted practical swords suited for cavalry combat. Kai swords were not as ornate as those of Bizen or Sōshū, but they are known to have prioritized durability and cutting power in actual warfare. The swordsmiths of Tōtōmi around Oyama Castle met the demand of the three great powers — Takeda, Imagawa, and Tokugawa — crafting swords tailored to each warlord's preferences. ## Warriors and Swords of Mikatagahara and Nagashino The Battle of Mikatagahara (1572) and the Battle of Nagashino (1575), which occurred during the era when Oyama Castle functioned as a front-line stronghold, were also pivotal encounters in Japan's Sengoku history, marking the transition from swords to firearms. The Battle of Nagashino in particular is regarded as a symbol of tactical revolution — cavalry units held at bay by concentrated firearm deployment — yet in reality, close-quarters combat with swords and spears remained decisive throughout. The swords carried by Takeda soldiers who trained and resupplied at Oyama Castle are, in essence, witnesses to this historical turning point, standing at the core of Oyama Castle's historical significance.
Highlights
- Mikazuki-bori crescent moats and maru-umadashi barbicans (National Historic Site) — finest surviving Takeda earthworks
- Takeda Katsuyori's front-line stronghold — feel the Takeda-Tokugawa rivalry for Tōtōmi Province
- Oyama Castle mock donjon and museum — Takeda fortification techniques and Sengoku Tōtōmi history
- Views of the Ōi River valley and Mount Fuji from the donjon
- Day-trip combination with Tanaka Castle and Kakegawa Castle — Sengoku Shizuoka circuit
* Opening hours and admission fees are subject to change. Please check the official website before visiting.