Reginald Guy Walker, Jr. was born on December 5, 1924, in Nashua, New Hampshire. Raised on Twin Elm Farm in Milford, Walker left high school early to support the war effort, receiving a War Emergency Diploma from Milford High School. He enlisted in the United States Marine Corps on January 29, 1943, during the height of World War II.

After completing his initial training at Parris Island and specialized radio instruction at Camp Lejeune, Walker was assigned to the 3rd Marine Division. Serving as a radio and telephone operator with the Weapons Company, 3rd Amphibious Tractor Battalion, he deployed to the Pacific Theater in 1944.

Walker saw significant combat during the campaigns in Guam and the Mariana Islands. In 1945, he participated in the Battle of Iwo Jima. His unit was instrumental in the assaults on strategic airfields and the push toward Mount Suribachi, maintaining vital communications under heavy enemy fire. For his actions in these theaters, he was awarded a service medal with three bronze stars. He was honorably discharged from active duty on December 17, 1945.

Following the war, Walker returned to New Hampshire, married Norma Jean Gerry in 1948, and pursued higher education, eventually earning a degree from Northeastern University. His professional career focused on defense electronics at Sanders Associates. However, his military service did not end with World War II; Walker reenlisted in the Marine Corps Reserve and later transitioned to the New Hampshire Army National Guard, where he rose through the ranks to retire as a colonel.