Kiyomori exported silver produced in Ise Province which was his power base and opened and cut Ondo no seto in Aki Province and so on to secure the channel in Seto Inland Sea and further he took over the right of foreign relations of Dazai-fu.
清盛は勢力基盤であった伊勢国で産出する銀などを輸出し、安芸国の音戸瀬戸を開削するなど瀬戸内海航路を確保し、さらに大宰府の対外交渉権の接収をおこなった。