On October 9th, 1941 in Harrisburg, Pa Ruby left his life working in the mines and enlisted in the Army. Upon joining the Army he became part of the 502nd Parachute Infantry Regiment in CoA all of which is part of the 101st Airborne Division. As part of the 502nd Parachute Infantry Regiment Ruby would do air assaults and parachute infantry as a main focus. Being a Parachute Infantry Regiment the 502nd used parachutes to drop in on places. On June 20th, 1944 at the rank of a Private, David Ruby was killed in action. A Private is the first rank in the US Army meaning that their responsibility is mostly to follow orders of higher ranking officers.

With the 502nd Parachute Infantry Regiment Ruby went to the European Theater. He spent time in France and was in the Carentan Peninsula for D-Day. In Normandy, the mission was to secure two northern causeways going inland from Utah Beach and to also destroy a battery of  German 122 mm Howitzers near Saint-Martin-de-Varreville, France. France is far quite far away from the 502nd's headquarters in Fort Benning, Georgia. The regiment originally started out as a Parachute Test Platoon with 48 men. On July 1st, 1941 the platoon was made into a Parachute Infantry Battalion commanded by Major George P. Howell and became based out of Fort Benning. It wasn't until March 2nd, 1942 that the Battalion became a Regiment under the command of the then Lt. Col. George P. Howell. 

502nd Parachute Infantry Regiment Motto: Strike, I fight where I am told, and win where I fight

502nd Parachute Infantry Regiment Nicknames: "Five-Oh-Deuce" & "The Deuce"