Bobbers and pirates appeared frequently, but the imperial court and kokushi could not cope with the situation using the gundan-soldier system that had become a dead letter and were forced to take a new measure to combat them.
群盗海賊の頻発に対し、朝廷と国司は、ほとんど形骸化した軍団兵士制では満足のいく対応ができなかったため、別の鎮圧方策をとる必要に迫られていた。