When the Hokuetsu War broke out, Kuroda thought that they should make the Echigo-Nagaoka clan surrender and employ Tsugunosuke KAWAI, and sent a letter to Kawai but it did not reach him.
北越戦争に際して、黒田は越後長岡藩を降伏させて河井継之助を登用すべきと考え、河井に書簡を送ったが届かなかった。