 The signing of this treaty occurred on two years after the Soviet-Japan War, and was of vital concern for proponents of the "Nanshin-ron" southern expansion doctrine within the Japanese government and military, as it enabled more troops to be deployed for the Japanese expansion into southeast Asia.On the same day, Tatekawa signed a separate treaty in which the Soviet Union pledged to respect the territorial integrity and inviolability of Manchukuo, and in which Japan pledged the same to respect the Soviet hegemony over the People's Republic of Mongolia.He remained ambassador until March 1942, when he had to return to Japan due to health problems.