The above isn't completely true. For many years the Army has been sponsoring Neurosurgery Residents at both University of Florida and University of Texas Health Science Center San Antonio. The spots are fully funded and the commitment is the same as for completing your residency at Walter Reed.
Additionally, the acuity and case numbers are going up because they are pulling in everyone who has Tricare Prime and under age 65. They are also starting to take over some VA patients also. All of these led SAMMC to have over 800 Neurosurgical cases last year.
I recall back in my residency days I had to do a month of a neurosurgery rotation. After rounds, I was forced to go to the cafeteria and eat breakfast with the team, which consisted of myself, a surgery intern, an active duty neurosurgeon, and a reservist neurosurgeon that was actived on a backfill, but happened to work as an attending at a university program. The breakfast conversation went something like this:
Intern: Dr. X, when you did your training at Walter Reed, did you get a lot of autonomy?
Dr. X.: When I was a chief resident, I did about 300 surgeries all by myself without an attending (in a cocky arrogant tone).
Backfilling Reservist: Huh, is that all? My resident do at least 1000 or more in their chief year, hell they do so much surgery in their chief year that they get sick of the OR.
Dr. X: (who is now taken aback and had the smiled wiped off his face): Well-----, well-----, ugh, do they do them alone without an attending?
Backfilling Reservist: Yeah
Dr. X: (now stunned and shut up, for once)