Ammunition or other things left behind is not handed over to the enemy - it is blown up. Peak oil is not an energy crisis. It is a liquid fuel crisis.
As for the desert route - with what trucks, exactly?
The big airports will be the first missile targets, and as soon as those are gone - and it's wonderfully easy to crater a runaway - the supply lines are cut and the clock is ticking.
Best of luck with a quick getaway after that.
