Lots of good suggestions, but I would like to point out that "Duty, Honor, Courage" is the motto of the 40th Infantry Divsion, my parent organization these days. I think that motto would be real good for you ckim715 as you will be in very good company - especially as a soon to be Infantryman HOOAH!
Another alternative would be Pro Liberate Patriae - For the Liberty of My Country.
Do decide carefully - as Acerbus pointed out this will be with you for awhile