From July 1941 to February 1942, "Suwa Maru" was employed as a troop transport used primarily to shuttle troops and supplies from Manchukuo and various ports in Japan and Taiwan to points along the China coast and to French Indochina. On 18 February 1942, she was one of 56 transports assigned to the Japanese force for the Japanese invasion of Java. On the successful completion of her mission, she returned to Moji on 11 April. On 18 April, she was released back to NYK but was then requisitioned by the Imperial Japanese Navy on 8 August and attached to Kure Naval District. She spent the remainder of the year shuttling men and material between Japan and Truk, the Marshall Islands, Kavieng on New Ireland, and Rabaul.