Applying for aviation training in 1925, he went to Naval Aeronautical Station Pensacola, Florida, for instruction, but was subsequently returned to duty with ground units.

A first lieutenant at the time, he earned his first Navy Cross for leading 12 Marines against 100 bandits in a night attack to break up a threat to his garrison.

Returning to the United States in 1933, Captain Carlson served as executive officer of the Marine Corps Detachment at President Roosevelt's alternative White House and vacation retreat at Warm Springs, Georgia, where he became closely acquainted with President Franklin D. Roosevelt and his son James.

Shortly afterward he was transferred to the Marine detachment, American Legation, Peiping, China, where he served as adjutant and studied the Chinese language.

Traveling thousands of miles through the interior of China with the communist guerrillas, often on foot and horseback over the most hazardous terrain, he lived under the same primitive conditions.

[3] Carlson often had leftwing political views, prompting General David M. Shoup to say of him, "He may be red, but he's not yellow.

Carlson was so impressed with the danger of Japanese aggression in the Far East that in 1939, he resigned his commission as a captain in order to be free to write and lecture on that subject.

When the danger he foresaw neared reality in 1941, Carlson applied to be recommissioned in the Marine Corps and was accepted with the rank of major.

In 1942, he was placed in command of the Second Marine Raider Battalion with the rank of lieutenant colonel, a new combat organization whose creation he influenced.

Drawing on his time in China and his experience in having gone back and forth between officer and enlisted status in both the Army and the Marine Corps that this was not in the best interests of the service, Carlson radically reformed the raider battalion along much more egalitarian lines.

[6] Carlson was soon ordered back to the United States for medical treatment of malaria and jaundice, and served as a technical advisor to Walter Wanger's Gung Ho!

He subsequently returned to the Pacific campaign and participated in the Battle of Tarawa in November 1943, as an observer, and was cited for volunteering to carry vital information through enemy fire from an advanced post to division headquarters.

He was advanced to the rank of brigadier general on the retired list at that time for having been specially commended for the performance of duty in actual combat.