On 23 November 1943, the U.S. Marine landing on Tarawa Atoll emphasized the need for hydrographic reconnaissance and underwater demolition of obstacles prior to any amphibious landing. After Tarawa, 30 officers and 150 enlisted men were moved to Waimanalo Amphibious Training Base to form the nucleus of a demolition training program. This group became Underwater Demolition Teams (UDT) ONE and TWO.In February 1944, the Naval Combat Demolition Training and Experimental Base was established at Kihei, Maui, next to the Amphibious Base at Kamaole.