I have read that Saturn I was started to meet the special requirements of DoD. The question is: Are there any records available which clarify / spell out WHY " Department of Defense (DoD) needed a heavy-lift vehicle to orbit a new class of communications and "other" satellites, such as to call for a vehicle capable of putting 20,000 to 40,000 pounds (9,100 to 18,100 kg) into orbit ...."
The article Cluster's Last Stand about Saturn 1 development states that the military's goals were
orbiting large communications satellites, manned space stations and even developing the strangelove-esque atomic moon bases under Project Horizon.
was a 1959 study to determine the feasibility of constructing a scientific / military base on the Moon, at a time when the U.S. Department of the Army, Department of the Navy, and Department of the Air Force had total responsibility for U.S. space program plans