You're giving yourself a month to lose 7 pounds. That is 2 pounds a week, which is in the range for successful Weight Watchers, for example. So just go very balanced, very controlled, nothing extreme but limit your calories to the range that will allow that (fitday helps you plan for a goal). Measure and log all your foods in the food log. Don't drink alcohol or caloric beverages - that can slow your progress.
Then, remember that if you join the army, you'll be doing a lot of strenuous activity and you'll be losing weight and getting fitter, so why stress about losing weight now?
Also, for your height and weight, your BMI is right in the middle of the normal range. No problem there...