It occurs to me that provision needs to be made for allied soldiers on the move in Iraq to shit in the desert while they slowly advance towards Bagdad. You don’t want to be caught squatting openly in the desert with you’re pants down . Peeing of course is no big deal unless you’re female. So are mobile toilets along for the ride? Is training provided for the quick swipe?
Well…speaking from my own experience…first, MRE’s tend to bind me up to the point of one shit every three days. It sucks. Second, dig a shallow cat hole within the perimeter, do your duty…er, doody. Wipe, with the one sheet method*. Cover the evidence. Take position so yer buddy can do his stuff.
*One sheet method: Take one sheet of TP. Fold into quarters and tear off one corner, thus leaving you with one sheet of TP with a hole in the middle, making sure to keep the torn off corner. Stick your index finger through the hole. Wipe with same finger in a front to back motion. Wrap TP around, now soiled, finger and wipe off poo. Discard or burn. Use torn off corner to remove poo lodged under fingernail. This is, of course, not the method of choice…but good in a tactical situation… 
And when that one dump in three days hits, well, my boss described it as what his dog must have felt the day after eating a peach, while passing the pit and howling.