Chashi

[1][2] Over 520 chashi have been identified in Hokkaidō, mostly in the eastern regions of the island; others are known from southern Sakhalin and the Kurils; similar phenomena such as the ostrogu of Kamchatka and the gorodische of northeast Asia may have developed independently.

The early Dutch explorer Maarten Gerritsz Vries described the chashi he encountered in eastern Hokkaidō in 1643:[3]These forts were made as follows: on the mountain on which they were placed was a small road steep to climb, and round on the four sides palisades were placed of the height … of 1½ man's length; within this stood two or three houses.

[1][5] Excavated chashi have revealed Japanese lacquerware, ceramics, ironware, and swords, as well as beads perhaps from Sakhalin; consumables included rice, sake, and tobacco.

[1] In 1668, disputes over deer, bear cubs, and a live crane lead to the Hae elder Chikunashi and his mother burning down the Shibuchari casi and killing the escapees.

[1] In response Shakushain sent the Urakawa Ainu to attack the Atsubetsu casi; driven off by musket fire they returned in force and captured it, after many of its defenders had left in search of food.