VR has been used not only in training military personnel, but also in providing therapy those who suffer from PTSD.
Lele, A., 2011. "Virtual reality and its military utility," Journal of Ambient Intelligence and Humanized Computing 4 (1): 17-26 (doi: 10.1007/s12652-011-0052-4).
Rizzo, A., T. D. Parsons, B. Lange, P. Kenny, J. G. Buckwalter, B. Rothbaum, J. Difede, J. Frazier, B. Newman, J. Williams, and G. Reger, 2011. "Virtual Reality Goes to War: A Brief Review of the Future of Military Behavioral Healthcare," Journal of Clinical Psychology in Medical Settings 18 (2): 176-187 (doi: 10.1007/s10880-011-9247-2).
Ter Haar, R. 2005. "Virtual Reality in the Military: Present and Future." 3rd Twente Student Conference on IT, Enschede.
While not very technical, great for understanding VR use in military:
https://www.vrs.org.uk/virtual-reality-military/
More in-depth, but not technical:
https://science.howstuffworks.com/virtual-military.htm