I think if you take any of the knives suggested you won't get wrong with. But are you not concerned how heavy it might be to carry a large and heavy knife? I was not in Iraq, but I worked in Middle East and I remember it is too hot there that you want to carry as little weight as possible. Plus, there are no large trees, except oasises, and a lot of open areas, so chopping is quite limited. When I was in desert, the wind was always blowing that within 5 minutes my equipment was full of sand. There are areas with compacted sand in desert, but mainly sand is not compacted and I saw rocky areas only near sea and mountains. Probably an ordinary shovel will work well as entrenching tool.
Regards,