Kasugayama Castle

Kasugayama Castle, located in Kasugayama, Nakayashiki, Kubiki District, Echigo Province (present-day Kasugayama-machi, Jōetsu City, Niigata Prefecture), was a medieval Japanese mountain castle widely known as the residence of the famous Sengoku warlord Uesugi Kenshin. The castle ruins are designated as a National Historic Site and are sometimes counted among the “Five Great Mountain Castles of Japan.”

It is said that the origins of Kasugayama Castle trace back to the Nanboku-chō period, when the Echigo provincial governor, the Uesugi clan, constructed it as a fortified satellite castle of the Echigo provincial headquarters. In 1507 (Eishō 4), deputy governor Nagao Tamekage ousted the provincial governor Uesugi Fusanori and installed Uesugi Sadazane, who then moved into the provincial headquarters, with the Nagao clan becoming lords of Kasugayama Castle.

Situated atop Mount Kasugayama in central Jōetsu, the castle was built to take advantage of the natural terrain, giving it the qualities of a natural fortress and making it extremely difficult to capture. Four successive lords—Nagao Tamekage, Nagao Harukage, Uesugi Kenshin (Nagao Kagetora), and Uesugi Kagekatsu—used it as their residence. However, after Uesugi Kagekatsu relocated to Aizu, Echigo came under the control of the Hori clan. Due to its inconvenient location deep in the mountains, which hindered administration and transportation, the Hori clan constructed Fukushima Castle near Naoetsu Port in 1607 (Keichō 12) and moved there, rendering Kasugayama Castle obsolete.

Also known as “Hachigamine Castle,” its name derives from Kasuga Shrine, which is said to have been established as a branch shrine of Kasuga Taisha in Nara. The shrine’s founding date is uncertain, with some accounts placing it in 958 (Tentoku 2), while others suggest it was built during the Uesugi clan’s castle construction or in the Bunmei era (1469–1486).

It is said that the main gate of nearby Rinsen-ji Temple was relocated from Kasugayama Castle’s rear gate (karametemon). Although there is no conclusive evidence, it is believed to date back at least to the Keichō era and may be the oldest surviving structure associated with the castle.

Notably, many old illustrations depicting stone walls and a tenshu (main keep) are largely imaginative; archaeological excavations have found no evidence of stone walls or roof tiles. In 2009, the first historically accurate restoration model was completed and displayed at the “Echigo Jōetsu Tenchijin Expo.”

To secure its domain and defend against external threats, numerous branch castles, forts, and residences were established around Kasugayama Castle, connected by military roads to form an extensive and tightly-knit defensive network.