jōsaku　城柵

1　A fence around a castle. See *saku 柵.

2　A general term for the earliest Japanese castles and fortifications. Jōsaku were most common in north-eastern Japan, where they were often sited on low hillocks or flatlands, and surrounded by a fence saku. They are believed to have had a dry moat *karabori 空堀 and earthen embankments *dorui 土塁. An early example is Nutari no ki 淳足柵, built in 647 at the mouth of the Shinano信濃 River, Niigata Prefecture. Jōsaku in northeastern Japan were built for colonization, serving as centers of local government.
Early fortresses were also built in southwest Japan to defend against foreign incursions. Here, Korean-type mountain castles chōsenshiki yamajiro 朝鮮式山城 were constructed at elevations of several hundred meters. The character for castle shiro 城, is usually associated with defensive barriers made of earthen embankments, while the character for fence saku suggests there were palisades of wood. Excavated sites in northeastern Japan, whose names include the characters shiro or saku, tend to support this distinction.