In Kokura-guchi, the alliance of Kyushu domains lead by the commander Nagamichi OGASAWARA and the Choshu clan lead by Shinsaku TAKASUGI and Aritomo YAMAGATA had several armed contacts across the Kanmon-kaikyo Strait (Ogura War).
小倉口では、総督・小笠原長行が指揮する九州諸藩と高杉晋作、山縣有朋ら率いる長州藩との戦闘（小倉戦争）が関門海峡をはさんで数度行われた。