Collins was aide-de-camp to the Commanding General of the Puerto Rico Department (his father) from 25 May to 31 December 1941. On 1 January 1942 he joined the 25th Field Artillery Battalion at Henry Barracks, Puerto Rico. He was promoted to captain in the Army of the United States on 1 February 1942, and commanded Battery B of the 25th from 1 March to 13 September 1942. He then returned to Fort Sill for a new division Officer's Training Course on 5 to 31 October, and was posted to the 331st Field Artillery Battalion of the newly formed 86th Infantry Division as its executive officer on 1 November. He was promoted to major in the Army of the United States on 4 December 1942. He was S-3 of the 86th Infantry Division artillery from 27 April to 23 May 1943, and Assistant G-3 of IX Corps from 24 May to 22 July 1943.[4]
On 26 October 1943, Collins assumed command of the 957th Field Artillery Battalion,[4] a North Dakota Army National Guard unit that had formerly been designated the 2nd Battalion, 188th Field Artillery Regiment, which had been inducted into Federal service on 1 April 1941. It was now equipped with M114 155 mm howitzers. The 957th embarked for the United Kingdom on the MV Britannic on 5 December 1943.[5] Collins was promoted to lieutenant colonel on 1 May 1944.[4] The 957th landed in France at Utah beach on 13 June 1944, and operated in support of divisions of VII Corps,[6] which was commanded by his uncle.[1]
The President of the United States of America, authorized by Act of Congress July 9, 1918, takes pleasure in presenting the Army Distinguished Service Medal to Brigadier General James Lawton Collins, Jr. (ASN: 0-21788), United States Army, for exceptionally meritorious and distinguished services to the Government of the United States, in a duty of great responsibility with Military Assistance Command, Vietnam, in the Republic of Vietnam, during the period from September 1964 to May 1966.[13]
Collins retired from the Army as a brigadier general in 1970, but was recalled to active duty as Chief of Military History. As such, he oversaw the production of a wide range of works on American military history. His works include War in Peacetime: The History and Lessons of Korea (1969), The Development and Training of the South Vietnamese Army, 1950–1972 (1975), Allied Participation in Vietnam (1975), The History of World War II (1979), War in Peace: The Marshall Cavendish Illustrated Encyclopedia of Postwar Conflict (1985), Israeli Paras (1986), and A Guide to the Study and Use of Military History (2000). He teamed up with British historian David G. Chandler to produce the D-Day Encyclopedia (1994). He was president of the U.S. Commission on Military History and the Council on America's Military Past. He was also a member of the International Commission of Military Historians that investigated the wartime of Kurt Waldheim, former President of Austria and Secretary-General of the United Nations.[1]
He and his wife Yolande de Mauduit Collins, the daughter of Georges, Vicomte de Mauduit, had four children: Corrine, Sharon, Suzanne and James Lawton Collins III.[15] The Brigadier General James L. Collins Book Prize for Military History was named in his honor.[12]
Cullum, George W. (1960). Biographical Register of the Officers and Graduates of the US Military Academy at West Point New York Since Its Establishment in 1802: Supplement Volume X 1950–1960. West Point, New York: West Point Alumni Foundation.