Oshi Castle

Oshi Castle, located in Gyōda, Saitama Prefecture, Japan, is a historic flatland-style fortress originally constructed in 1479 by Narita Akiyasu. Often referred to as Turtle Castle or the Floating Castle of Oshi due to its strategic placement amidst marshes and swamplands, it was renowned as one of the seven primary strongholds of the Kantō region. The site served as the political center for the 100,000 koku Oshi Domain during the Edo period under various daimyō families, benefiting significantly from its proximity to the Nakasendō highway and the Tone River, which facilitated trade and prosperity for the surrounding castle town.

The castle achieved legendary status during the late Sengoku period, specifically in 1590, when it withstood the famous Siege of Oshi. Despite Toyotomi Hideyoshi dispatching Ishida Mitsunari with an army of 23,000 troops to flood the defenses using an extensive system of dikes, the small garrison of samurai and local conscripts successfully held the impregnable position. They only surrendered after learning that their overlords had been defeated at the Siege of Odawara. This remarkable defense against overwhelming odds and engineered flooding remains the most significant event in the castle's military history, distinguishing it from other fortifications of the era.

Following the Meiji Restoration, the original structures were demolished in 1871, and the grounds were converted into a public park. However, to promote local tourism and preserve regional heritage, the main keep was reconstructed in 1988. Today, the site is open to the public and houses the Gyōda City Local History Museum within the rebuilt donjon. While the original buildings from the Edo period no longer stand, the reconstructed tower and surviving gates allow visitors to explore the legacy of this unique water-based fortress and its pivotal role in Japanese feudal history.