According to the National Archives enlistment records, Richard enlisted in the Army at Pittsburgh, PA on 27 September 1940 with an Infantry assignment.  He later volunteered for parachutist duty.

Initially assigned to the 507th PIR, Sgt Slagle was a member of the cadre team transferred to the 508th PIR on 16 October 1942.

On 5 November 1942 he was promoted to the grade of 1st Sergeant and held that rank through WWII.

He was discharged on 27 September 1945 at the Indiantown Gap Military Reservation, PA.

Slagel's military decorations include the Bronze Service Arrowhead device awarded for his participation in the Normandy assault