Pender enlisted in the U.S. Army at age 17 and later went through Officer Candidate School (OCS); he was a decorated Vietnam War combat veteran and served for 21 years, retiring at the rank of captain in 1976. Early in his military service, Pender took up athletics, where his incredible quickness was noticed in camp football games. His progress was remarkable and he was selected to the 1964 Olympic Team, but was hampered by injury and finished seventh in the 100 meters at Tokyo.