Chashi Form . The early Dutch explorer Maarten Gerritsz Vries described the " chashi " he encountered in eastern Hokkaidō in 1643 : 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 . There were large fir doors in the palisades with strong clamps ; when they were closed , two stout bars were passed through the clamps and thus fastened to them . At the two corners of these … palisades , a high scaffolding is made of fir planks , for a lookout . Competiton for resources . In 1604 Tokugawa Ieyasu granted exclusive trading rights with the Ainu to the Matsumae clan ; lacking an agricultural base , the domain was dependent on trade ; the Ainu in turn became increasingly dependent upon Japanese commodities and prestige goods . Excavated " chashi " have revealed Japanese lacquerware , ceramics , ironware , and swords , as well as beads perhaps from Sakhalin ; consumables included rice , sake , and tobacco . In return the Ainu traded products derived from bird , beast , and fish ; plants and medicines ; and goods imported via Sakhalin . However , " the market culture of the trading post … destroy [ ed ] the ecological balance … [ through ] overhunting and overfishing " . By the end of the following century , the depletion of natural stocks resulted in famine . Furthermore , " competition over animals and fisheries was at the heart of most Ainu conflicts " . Shakushain ' s Revolt . The and recount the internecine conflict of 1668 / 9 , which culminated in massacres of the Japanese , military intervention , and subjugation , in what is known as Shakushain ' s Revolt . According to the " Ezo hōki " , regional influence among the Ainu was based on " good land " , " many utensils " , charismatic authority , and physical strength . 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 . 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 . The conflict escalated the following year into fighting with the Japanese ; after his final surrender , Shukushain was killed and the Shibuchari " casi " again burned to the ground . Known " chashi " . Among the approximately five hundred and thirty " chashi " identified by archaeologists , the sites of eight have been designated national Historic Sites : the Otafunbe " chashi " ; Shibechari River " chashi " and Appetsu " chashi " ; Moshiriya " chashi " ; Yukuepira " chashi " ; Katsuragaoka " chashi " ; Nemuro Peninsula " chashi " ; and Tsurugataicharanke " chashi " . Others known include the Arashiyama " casi " , Harutoru " casi " , Onibishi ' s " casi " , Sarushina " casi " , Sashirui " casi " , Setanai " casi " , and Uraike " casi " . Although there are nineteen " chashi " on the Shiretoko Peninsula , it is inscribed as a Natural rather than a mixed Natural and Cultural UNESCO World Heritage Site . Functions . In addition to providing for defence against rival Ainu , " chashi " functioned as centres for gatherings and rituals . They also served as " visible symbols of chiefdom power " . According to narrative uepeker or folktales , Akkeshi and Nemuro Ainu attacked the Uraike " casi " in the hope of " fine treasure " ; other " chashi " were attacked by hungry Ainu looking for venison and dried salmon .