On 15 June the group participated in the first American Air Force attack on the Japanese Home Islands since the Doolittle raid in 1942 when it took part in the bombing of Yawata. Operating from bases in India, and at times staging through fields in China, the group struck such targets as transportation centers, naval installations, iron works, and aircraft plants in Burma, Thailand, China, Japan, Indonesia, and Formosa, receiving a Distinguished Unit Citation for bombing iron and steel works at Yawata, Japan, on 20 August 1944. From a staging field in Ceylon, the 40th mined waters near the port of Palembang, Sumatra, in August 1944.