Robert Ledder enlisted in the United States Navy in 1944.

After a series of extensive tests, Ledder was among a select few to be awarded a complete college education by the United States Navy. This program was designed to develop the future Officer Corps for the United States Navy. As a result, Ledder attended Baldwin Wallace College in Berea, Ohio, Notre Dame University in South Bend, Ind., and Cornell University in Ithaca, New York. He received his Bachelor of Science degree from Cornell in 1948.

Ledder was commissioned as an Ensign as part of the crew of the USS Duluth. In 1953, he resigned his commission and left the service.