Until May 31 , 1931 , Colonel Seishiro Itagaki , Lieutenant Colonel Kanji Ishiwara , Colonel Kenji Doihara , and Major Takayoshi Tanaka had completed plans for the incident .
Colonel Seishirō Itagaki , Lieutenant Colonel Kanji Ishiwara , Colonel Kenji Doihara , and Major Takayoshi Tanaka had completed plans for the incident by 31 May 1931 .