Mandato del Pacífico Sur
From June 1939, "Komahashi" was once again assigned to the Yokosuka Naval District, and assigned to surveying missions and patrols of the South Pacific Mandate area for the potential development of seaplane bases and naval harbors, and was serving in this capacity at the time of the attack on Pearl Harbor on 7 December 1941. At some time during 1941, she was also fitted with depth charge racks and six Type 96 25-mm AA guns.