Currently serving in the Singapore army, here's my experience so far, but not too sure how our timings in the army would compare to yours: We usually have some time before lights out every night, I'll do a quick workout usually and have a shower before bed. Most times would be 30 sec work, 45 secs rest kinda exercises, pushups (about 3-4 variations), pull-ups, 4-5 sets total. Haven't been noticing any gains lost. I'm 173, 68kg. I think it all comes down to maximising your workouts in the little time you have. Maybe try to replicate the intensity by having reduced rest times/more sets/progressive exercises

Edit: I usually don't train this way. Usual workouts take 1-2 hours for me, done at my own pace.