In December 1941, "Mogami" was tasked with the invasion of Sarawak, together with "Mikuma", covering landings of Japanese troops at Kuching. In February 1942, "Mogami" was assigned to cover the landings of Japanese troops in Java, Borneo and Sumatra. On 10 February, "Mogami" and were attacked by the submarine , which fired four torpedoes, all of which missed.