President Roosevelt's captain Evans Fordyce Carlson
http://en.wikipedia.org/wiki/Evans_Carlson
[edit] Second and third China tours
After his Warm Springs tour Carlson was posted to the 4th Marines in Shanghai. Shortly afterward he was transferred to the Marine Detachment, American Legation, Peiping, China, where he served as Adjutant and studied the Chinese language. In 1936, he returned to the United States via Japan. At home he served at Quantico while attending Marine Corps Schools, and studying International Law and Politics at George Washington University in Washington, D.C.
He went back to China for the third time in 1937 as an official student of the Chinese language and as a military observer with Chinese forces. There he was afforded the opportunity to learn the tactics of the Japanese soldier.
He met Edgar Snow in China and read Snow's Red Star Over China. This encounter led him to visit the Chinese communist troop headquarters in northern China, where he met Chinese Communist leaders such as Mao Zedong, Zhou Enlai and Deng Xiaoping. 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. He was impressed by the tactics used by Chinese Communist guerrillas to fight Japanese troops.
When he left China in 1938, he was commended by the Commander in Chief of the Asiatic Fleet for his services. He 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, he applied to be recommissioned in the Marine Corps and was accepted with the rank of major.
Carlson wrote books about his third tour in China when he was attached to the Chinese 8th Route Army:
Twin Stars of China, Dodd, Mead & Company, 1940.
The Chinese army its organization and military efficiency, International Secretariat, Institute of Pacific Relations, 1939. (ASIN B00089LO5S)
Evans F. Carlson on China at War, 1937–1941, China and U.S. Publication. (ASIN B0006F13D2)