If you are "stuck" you have to change your methods. Army seems to think distance will eventually improve speed and it just isn't true. You could run 10 minute miles for a year, and still not be able to do 8 minutes. They are useful only for the initial conditioning phase to prevent stress injuries (and maybe mental toughness).
If you want 6 minute miles, run 10mph until you are sucking air...then jog 6 mph (recovery pace) until you can sprint again. Alternate between training pace and recovery pace until your training time total 20 minutes. Do this 3x week. The benefit is as your recovery time decreases, you total workout time will decrease.
All that matters is that you have 1hr+ at the training pace. If you are under 30 and have no health problems, you could push this to 2 hours per week.
Understand vascularity and some adaptation takes 6+ weeks. Results will be slow. The good news is gains are easier when you are slow. 10 minute to 8 minute might take a few months, 6 minute to 5 minutes years.
Running is a skill. relax. A problem is running "harder" isn't actually faster. Form goes to shit (bouncing, short stride), upper body gets tense, breathing is shallow. It feels like it should be faster based on effort, but it isn't. Watch distance runners: they glide along the ground and their head barely moves up and down. Plus the reduction in stress makes running a lot more enjoyable.
You can practice this on a treadmill by running at a moderate pace, and consciously learning to relax upper body and extending stride...then increase by .1mph and repeat until you are as relaxed and easy breathing as before. You are training yourself to go faster with the same amount of effort. Take 30 seconds off your run at the exact same heart rate just by thinking?! 1SGs hate him!
I was no PT stud, but 12:30 (2 mile)/90pu/90su was no problem once I figured out how to train. I went from 15 minute 2 mile to 13:30 (Age 35, Fallujah in July), to 12:19 less than a year later. Once we started independent "release runs" I improved faster and hurt less. 6 mile company runs were our Fri tradition and that short stepping really hurt. 8 mile solo runs under 60 minutes were much easier. I watched the same guys struggle for years, once I became NCO and could lead PLT pt, things improved.
None of this is new information. The internet has a million videos on running form, etc. But for some reason the wheel gets reinvented every time. NCOs (and X-country coaches) seem to be more concerned with total miles , than pace. it makes like harder.
100 sit-ups (do they still do those?) in 2 minutes is also just a specific training method.
Hope this helps you...and your Soldiers when you get them. Good luck. Consult your doctor.