Kannonji Castle

Kannonji Castle is a mountain castle located in Azuchi Town, Ōmihachiman City, Shiga Prefecture, Japan. Built on Mount Kinugasa (elevation 432.9 meters), it served as the residence and final stronghold of the Sasaki clan (later the Rokkaku clan), who were active from the Nanbokuchō period to the Sengoku period. Today, the castle ruins are designated as a National Historic Site of Japan and are regarded as one of the most important remains for studying medieval Japanese castles.

Kannonji Castle is a representative example of medieval mountain castles in Japan. With its steep terrain, it was strategically positioned on the eastern shore of Lake Biwa, at the crossroads of the Tōsandō highway and Happū road, allowing control over surrounding land and water routes. Its main structures were concentrated on the southern slope of the mountain, with numerous terraced baileys (kuruwa) spread across the area, where vassals and local lords are said to have had their residences. Remarkably, Kannonji Castle was one of the rare examples in medieval Japan to make extensive use of stone walls, a feature uncommon before the construction of Azuchi Castle.

At the foot of the castle once lay a castle town called Ishidera, which prospered as a commercial hub under the "rakuichi" (free market) system during the Tenbun era (early 16th century), reflecting the Rokkaku clan’s political and economic influence.

The exact date of the castle’s construction is unclear, but according to the Taiheiki, Rokkaku Yorii of the Northern Court forces was already stationed here in 1335 (Kenmu 2) to resist an attack by the Southern Court general Kitabatake Akiie, suggesting the castle already had a basic form at the time. In 1351 (Kan'ō 2), when Ashikaga Tadayoshi allied with the Southern Court and defeated the forces of Ashikaga Takauji in Ōmi, Sasaki Dōyo and Rokkaku Yorii retreated to Kannonji Castle, which was then also referred to as “Sasaki Castle.”

Throughout the Sengoku period, Kannonji Castle remained the Rokkaku clan’s main base until around 1570, when Oda Nobunaga invaded Ōmi. The Rokkaku clan was defeated, and Kannonji Castle was subsequently abandoned amid political upheaval. Soon after, Nobunaga constructed the famous Azuchi Castle on neighboring Mount Azuchi, shifting the political center of Ōmi from Kannonji to Azuchi.

Today, although much of Kannonji Castle is in ruins, visitors climbing Mount Kinugasa can still see its vast stone walls and the remains of baileys, while enjoying panoramic views of Lake Biwa and the surrounding plains. The site is popular among history enthusiasts and hikers. Nearby Kannon Shōji Temple, which shares its name with the castle, is traditionally regarded as part of the castle complex or as a military outpost.