On 13 January, "Monssen" departed Luzon, escorted empty transports to Leyte, and then proceeded on to Ulithi, where she joined TG 58.5, the fast carrier night group. The force sortied 10 February and set a course for the Japanese homeland. On the 16th and 17th, strikes were conducted on the Tokyo area to prevent reinforcements from being sent to aid the Imperial forces in the Bonin and Volcano Islands. By the 19th, they were off Iwo Jima, providing support for the American troops embattled there. "Monssen" remained in the Volcanos, screening the carriers and providing gunfire support for the land forces, until 9 March, when she returned to Ulithi. On 14 March, she again sortied with TF 58 for strikes on the enemy's home islands. On the 18th, the carriers sent their planes against Kyūshū and, on the 19th, against the Kure Naval Base, after which "Monssen" retired with the damaged .