His first assignment was with the 30th Infantry Regiment, then serving in Alaska. He did not see any active service during World War I but, by now a captain, he served in Germany from 1919 to 1923 as commander of the 1st Battalion, 8th Infantry Regiment which was the last formation to leave Germany.
The United States entered World War II in December 1941, by which time Barton was a temporary colonel, having been promoted to that rank on February 14.[1]
Having gained for himself a reputation as an excellent trainer of troops, Barton dedicated himself to training the men under his command for their ultimate test, the Alliedinvasion of Normandy, which would be their baptism of fire. The division conducted training in amphibious landings at Camp Gordon Johnston, Florida, and continued to do so after it left the United States, arriving in January 1944 in England, from where the Allies would launch the invasion, then scheduled for May 1944. Once there, training in amphibious landings continued, most notably at Slapton Sands in Devon.[3]
The Allies' plan for the invasion was for the U.S. VII Corps, under Major General J. Lawton Collins, to seize and hold Utah Beach, with Barton's 4th Division as its spearhead. The division's leading units began landing on Utah Beach early in the morning on June 6, with Barton himself arriving ashore in the afternoon. In contrast to Omaha Beach, where the Germans had put a fierce defense and inflicted heavy casualties on the Americans, Utah saw only light resistance. Despite this, Barton was concerned about getting his men and equipment off of Utah and inland to link up with the American airborne forces which had landed in Normandy in the early hours of the morning (see American airborne landings in Normandy).[3] The terrain behind Utah was flooded, which made the move inland more difficult, and meant that the causeways were the only escape inland. During one point in the afternoon Barton himself began directing traffic through the only open causeway off the beach. His worries were lessened when the Allies opened up other exits.[3]
Barton then began leading his division inland where it relieved troops of the 82nd Airborne Division who had become isolated at Sainte-Mère-Église. In the next few days Barton's division fought to enlarge the Allies' beachhead in Normandy, with the Germans putting up their usual stubborn resistance. A story of this period in the fighting in Normandy tells of Barton visiting a unit of his division to encourage the men. Upon informing them that the Germans opposite them were not first-rate, the unit's intelligence officer countered by stating that the Germans should be put on the distribution list as they apparently did not realize they were second-rate.[3]
During the war he became friends with Ernest Hemingway who sought his favor as the war correspondent assigned to the division and the two corresponded after.
Hemingway wrote to Barton:
You had one of the greatest divisions in American military history.
During the Battle of Hürtgen Forest on the Weisser Weh stream near Grosshau, Germany General Barton gave up his belt for tourniquet material to medic Russell J. York of his division at York's request. Lives were saved, and a Silver Star was personally awarded to Technician (Medical) 4th Grade York by General Barton for his actions.