If you had deep waves in your hair that was the curl pattern you had at that time. your hair may changes curl patterns throughout your life. babies sometimes are born with curly or straight hair then it might change to the opposite pattern when the get older. Also around the age of twenty your hair might change again. It also might change when your get in your later years such as 40's and 50's. sometimes these changes occur with the curl pattern, it can also change the hair texture(fine or wiry). I would have to say that you probably entered the army around one of these age groups an hair curl pattern changed on it;s own.And due to the extremely short hair cuts, your hair was not long enough for you to see the changes. Also any cutting you do to your hair does not effect the structure of your hair, Because the structural makeup lies in your hair follicles that is in the skin which will not be effected by haircuts. to be sure if your texture has changed, check your curl pattern when your hair has grown out at least few inches from your scalp, so you can see the pattern.
If you are unhappy with the lack of curl pattern you have now, you can check into a perm.