On 13 June 1944 the Combined Fleet activated Operation A-Go for the defense of the Mariana Islands, and that day the commander of the 6th Fleet, Vice Admiral Takeo Takagi, ordered all available Japanese submarines, including "Ro-41", to deploy east of the Marianas. The Marianas campaign began with the U.S. invasion of Saipan on 15 June 1944, and on 16 June the 6th Fleet ordered most of the submarines, again including "Ro-41", to withdraw from the Marianas.