I've been to Iraq twice...a 6" knife is pushing the upper limits of what they will be able to carry, and in some cases it will have to be left behind.
An AD is just too small, stay between a Meaner and a SAR 4/5 size knife and he'll be able to use and carry it every where.
It's all about public image in Iraq right now, you can't look threating when you're out in public.
A 4" or 5" knife can be tucked away under a belt or strap and will be accepted, larger knifes don't have the right image.
Meaners are nice but I would get something in a .22" - .27" range, it will be used to pry open ammo cases, dig with, cut food, play chicken, cut banding straps, used as a handle to move razor wire, etc, etc...
If it were me doing it over again, a SAR$4 would be my choice.
Not too long, heavy blade, that serration stuff on the spine to hold on to stuff while you're moving it, heavy handle to beat in pegs or beat open crates, SAR 4 would be sweet and it's only $327 Bucks.
Also a good pair of pliers with heat treated cutting edge, he's a grunt, he'll be bending wire either in HESCO's or razor wire.
The razor wire is hardened and will destroy cheap pliers and the best multi tools with the first snip.