In 664, they built a castle in the province of Chikushi in Kyushu to defend Dazaifu (the political center in northern Kyushu at the time) and forts in Tsushima, Oki and Chikushi with sakimori (coastguards) stationed there.
664年（天智2年）筑紫に大宰府を守る水城を造り、対馬・隠岐・筑紫に防人や烽を置いた。