I used to be in Air Force. That has nothing to do with anything, I'm just saying. You have two months to prepare. That is way more than enough time.
Whatever you decide to do, do not increase your mileage any more than 10% per week. I ran twice a day in Baghdad. I started at two miles per session and before I knew it I was running 8 or more miles a day.
You are going to have to sacrifice some of your personal time for this mission to be accomplished. Morning training is best, but if you can't muster up the motivation to go to the gym early, any time of the day is better than none. Go to the free gym on base, and hop on a treadmill. You need 1.5 miles, so that is what you shoot for. Fitness should be an overall goal, but training for a specific one will suffice for now.
You run that 1.5 miles as fast as you can manage, but on an incline. You should run at least a 1.0 incline regardless, as otherwise the motor and belt are making it easier than running on asphalt. Start there. Run 1.5 miles every day at a 1.0 incline. The next week, run the same distance every day at a 2.0 incline. The third week, keep the incline at 2.0 and bump the distance a bit. Keep seesawing the incline and distance progressively higher until you are running 2 miles at a 3.0 incline or better. By the time test day rolls around, and you get to run 1.5 miles on open ground it will be easy as pie.