For outstanding service as assistant chief of staff, G-3, Tactical Group One, during the planning and execution of the Marshall Islands invasion, Greene was awarded his first Legion of Merit with Combat "V". Following the disbanding of the group in March 1944, he joined the 2nd Marine Division as G-3, earning a second Legion of Merit for outstanding service in this capacity prior to and during combat on Saipan and Tinian. He remained with the 2nd Division until his return to the United States in September 1944.