By D-Day on June 6, 1944, Ehlers was a staff sergeant and squad leader in the 18th Infantry Regiment, 1st Infantry Division. His squad, part of the invasion's second wave, waited off shore in a Landing Craft, Infantry, while the first group of soldiers landed. When the first wave became pinned down on the beach, his unit was transferred to a Higgins boat and sent forward early to assist. They fought their way off the beach and by June 9 were near the town of Goville, inland. On that day, he led his unit's attack against German forces and single-handedly defeated several enemy machine gun nests. The next day the platoon came under heavy fire. Ehlers was wounded, but managed to cover the platoon's withdrawal; this included carrying a wounded automatic rifleman to safety and running back through enemy fire to retrieve his Browning Automatic Rifle. After treatment of his wounds, Ehlers refused to be evacuated and continued to lead his squad. For his actions he was awarded the Medal of Honor five months later on 11 December 1944. He was decorated at Paris in the office of Lt. Gen. John C. H. Lee, Commanding General, Communications Zone, ETO. By this time Ehlers had received a battlefield commission to 2nd lieutenant.