Carlson had been a soldier in the Punitive Expedition to capture Pancho Villa in Mexico and World War I, became a Marine officer during the American occupation of Nicaragua, and served as an Intelligence Officer of the 4th Marines in China. He had seen the tactics and strategy of Communist Chinese irregulars, Zhū Dé and the Eighth Route Army in particular, as they fought the occupying Japanese and became enthralled with their version of guerrilla warfare. In 1933 Carlson had commanded the Marine Detachment at the Warm Springs, Georgia vacation retreat of President Roosevelt, where he formed a close friendship with both Franklin D. Roosevelt and his son James. Carlson resigned from the Marines to speak to American businessmen to warn them against providing materials to Japan. Carlson rejoined the Marines in April 1941, gaining a commission from the Commandant as a reserve major. Carlson still had the President's ear as well as FDR's son James Roosevelt, who was now a Marine Captain and was his friend and protégé. The Raiders were given the best of the Marines' equipment, and were handpicked from available volunteers. The two units approached their common mission from different directions. Carlson used egalitarian and team-building methods learned from the Communists during his years in China: he treated officers and enlisted men with minimum regard to rank as leaders and fighters, gave his men "ethical indoctrination," describing for each man what he was fighting for and why, and used the Chinese phrase "Gung-ho!" as a motivational slogan. He also eschewed standard Marine Corps organization, forming six rifle companies of two platoons each, and innovating 3-man "fire teams" as its basic unit. Edson's battalion, however, more closely followed standard Marine Corps doctrine in training, organization, and discipline. Both Raider battalions were put into action at roughly the same time. On 7 August 1942, Edson's 1st Raider Battalion, assigned to the 1st Marine Division, landed on Tulagi in the British Solomon Islands Protectorate as the opening phase of the Guadalcanal Campaign. After the capture of Tulagi, the Raiders were moved to Guadalcanal to defend Henderson Field. One of their most notable engagements was the "Battle of Edson's Ridge", where the 1st Raiders, remnants of the 1st Parachute Battalion, and the 2nd Battalion 5th Marines scored a major defensive victory over Imperial Japanese Army forces on the night of September 13–14. Out of the action both Edson and Major Kenneth D. Bailey were awarded the Medal of Honor, the latter posthumously.