Funk joined the United States Army from Wilkinsburg, Pennsylvania in June 1941. The following year, after the United States entered World War II, he volunteered for the paratroopers, part of the U.S. Army's newly created airborne forces. After completing his training and earning his jump wings, he was assigned to Company 'C' of the 1st Battalion, 508th Parachute Infantry Regiment (508th PIR), then stationed in Camp Blanding, Florida. He was to serve with the 508th throughout the war and went with the regiment to England in late 1943, where they became part of the veteran 82nd Airborne Division. He jumped into Normandy with the 508th on D-Day, June 6, 1944, later taking part in Operation Market Garden in September, and later in the Battle of the Bulge in December.