Flint was also commended by his commander after he prevented the detonation of a trainload of high explosives during a fire at an ammunition dump by taking over the controls of a switch engine and maneuvering the train through the flames to safety. Post-World War I Flint returned to the United States in 1921, and his post-war assignments included: instructor at the U.S. Army Cavalry School; attendance at the General Service School and U.S. Army Command and General Staff College, and professor of military science at the New Mexico Military Institute. He attended Ecole Supérieure de Guerre in Paris and became fluent in French. Flint also performed staff duty on the office of the Chief of Cavalry and at the Air Corps Tactical School. After serving with the 1st Cavalry Regiment at Fort Knox, Kentucky from 1933 to 1935, he was promoted to lieutenant colonel as head of the ROTC program at the University of Illinois. From 1939 to 1941, Flint served with the 5th Cavalry Regiment. The last month of 1941 saw the United States officially enter World War II. World War II Assigned to the 2nd Armored Division, Flint commanded the 56th Armored Infantry Regiment, for which he received the Legion of Merit. Later assigned to the U.S. II Corps, Flint took part in the invasion of North Africa (Operation Torch) as part of the corps G-3 (operations and training) staff and as a liaison officer to the French headquarters in Algiers. For his service with the French, Flint received the Legion of Honor (Chevalier). Hoping for a combat assignment despite his advanced age, Flint approached the new II Corps commander, Major General Omar Bradley directly in April 1943, shortly before the Allied invasion of Sicily (Operation Husky) and requested combat duty. Soon afterwards, Flint was assigned as commander of the Headquarters Detachment of the 2nd Armored Division. 39th Infantry Regiment In mid-July 1943, Flint was appointed to command the 39th Infantry Regiment while fighting was still ongoing in Sicily. The 39th Infantry had fought in North Africa and Sicily, and had sustained numerous casualties. In addition, the regimental commander had to be evacuated after breaking his leg in an accident. The 39th Infantry was a unit of the 9th Infantry Division; when division commander Manton Eddy requested a new commander for the 39th Infantry Regiment, Bradley recommended Flint, and Eddy accepted. Flint took immediate steps to restore