Qualla: Oshi Castle

Oshi Castle: Introduction

Mon, 16 Feb 2026 00:00:00 GMT

Photo credit Saigen Jiro, CC0. They tried to drown the castle. In the summer of 1590, the warlord Ishida Mitsunari -- commanding 23,000 soldiers on behalf of Japan's most powerful man, Toyotomi Hideyoshi -- ordered his troops to build 28 kilometers of earthen dikes around Oshi Castle and divert the waters of the nearby rivers to flood the defenders out. It was an ambitious plan modeled on Hideyoshi's own famous siege of Takamatsu eight years earlier. But the marshes that surrounded Oshi had always been its greatest weapon, and the water rose against the besiegers as much as the besieged. The castle held. Inside its walls, 619 samurai and 2,000 local conscripts -- including the castellan's daughter Kaihime -- waited out the deluge for over a month. When they finally surrendered, it was not because the walls had fallen but because word arrived that their overlords, the Hojo clan, had been defeated at Odawara. Oshi Castle emerged from the ordeal with a nickname that endures to this day: the Floating Castle.

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Image: Saigen Jiro | CC0

Oshi Castle: Built on Borrowed Ground

Mon, 16 Feb 2026 00:00:00 GMT

Photo credit kamoseiro, CC BY-SA 3.0. Narita Akiyasu completed Oshi Castle around 1479 on a low rise near the Tone River, threading its walls and baileys through the marshes and swamplands that blanketed the northern Kanto Plain. Those wetlands were not obstacles -- they were the design. The bogs and flooded paddies ...

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Image: kamoseiro | CC BY-SA 3.0

Oshi Castle: The Siege That Made a Castle Famous

Mon, 16 Feb 2026 00:00:00 GMT

Photo credit Alexrk2, CC BY-SA 3.0. When Toyotomi Hideyoshi launched his massive campaign against the Hojo clan in 1590, Oshi Castle's lord Narita Ujinaga was already at Odawara with his best warriors, leaving the home fortress desperately undermanned. Ishida Mitsunari arrived with 23,000 troops expecting a quick c...

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Image: Alexrk2 | CC BY-SA 3.0

Oshi Castle: The Aftermath That Changed Japan

Mon, 16 Feb 2026 00:00:00 GMT

Photo credit Ebiebi2, Public domain. The siege of Oshi ended not with a breach but with a message. When news reached the defenders that Narita Ujinaga had surrendered at Odawara, further resistance lost its purpose. The garrison laid down its arms. But the consequences of this drawn-out stalemate rippled far beyond ...

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Image: Ebiebi2 | Public domain

Oshi Castle: From Fortress to Park

Mon, 16 Feb 2026 00:00:00 GMT

Photo credit 京浜にけ, CC BY-SA 3.0. After 1590, Tokugawa Ieyasu claimed the Kanto region as his own and rebuilt Oshi Castle as the seat of the 100,000 koku Oshi Domain. For the next 270 years, the castle served as an administrative center under a rotating succession of daimyo from the Matsudaira and Abe clans. The ...

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Image: 京浜にけ | CC BY-SA 3.0