I broke the rears loose at work with a 3/4" impact on 140psi shop air, and they were tough... The fronts I did at home later... Couldn't budge them with a 3/4" breaker bar and a 4' pipe... A little heat on each with a map gas torch and I could loosen them but the first 1/4 turn was still not easy... they were TIGHT!! I think the military is really over-torquing the nuts... That combined with age makes them very difficult to remove.
On reassembly, I used a little grease on each and ran them tight with my 1/2" impact at 80psi on shop air, and I can pretty easily loosen them even with the pathetically short breaker handle that came with the truck. My gun has to be getting them past 200ftlb, so I think that's plenty tight, and servicable if I have a flat. Breaking them loose, I was PUTTING OUT, so let's say I can put out 200lb of lifting on the end of a 4' pipe. That's 800ftlb to break them loose, after heat...
C