Richard Dolan is a non-academic historian who has studied both acknowledge and alleged military programs in space. IMO, he does a good job of steering clear of the 'little green men' / 'space brothers' material and focuses on what can be gleaned from FOIA requests, declassified govt docs, etc.
He describes a situation where the USAF, Navy, NRO and probably a few other gov/mil agencies have each developed their own independent space programs, sometimes competing with one another more than collaborating the way they theoretically should.
Here is a pdf that summarizes some of his research on it all. My take on the Space Force initiative is that POTUS is trying to unite these various mil/intel space programs and to do so in a way that brings them under constitutional controls.