completed the course in May 1940, then took command of the 1st Chemical Company, 1st Marine Brigade, sailing with it that October for Guantanamo Bay, Cuba. While there, the brigade was redesignated the 1st Marine Division. Returning with his unit in April 1941, Greene served at Quantico and New River (later Camp Lejeune), North Carolina, as assistant operations officer, 1st Marine Division. In November 1941, he was ordered to London, England, as a Special Naval Observer. During that assignment, he attended the British Amphibious Warfare School in Inverary, Scotland, and the Royal Engineer Demolitions School in Ripon, York. He was promoted to major in January 1942 and returned to the United States the following month. Named Assistant Chief of Staff, G-3, 3rd Marine Brigade, in March 1942, Greene sailed with the brigade for Upolu, Western Samoa, the following month. He was promoted to lieutenant colonel in August 1942 and remained on Samoa until November 1943 when he joined the V Amphibious Corps in Hawaii. 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. In October 1944, Greene was appointed officer in charge, G-3, Operations, Division of Plans and Policies, Headquarters Marine Corps (HQMC). He held that post until July 1945, then served as executive officer, Special Services Branch, Personnel Department. In April 1946, he was ordered to Little Creek, Virginia, as G-3, Troop Training Unit, Amphibious Training Command, United States Atlantic Fleet. While there, he was promoted to colonel in February 1948, with rank from August 1947. Detached from Little Creek in June 1948, Greene reported to Pearl Harbor that August as G-3, Fleet Marine Force (FMF), Pacific. He returned from that assignment in June 1950 and for the next two years was Chief of the Combined Arms Section, Marine Corps Schools, Quantico. He also served briefly as Chief of the Coordination and Evaluation Section there, before entering the National War College, Washington, in August 1952. He graduated in June 1953 and