Might be better to look at it as a 'Post Apocalypse' mod.

Then the armies can be armed with improvised weaponry. If there were no real production facilities left, then the armies would be equipped with whatever they could lay their hands on. Homemade weapons..... spears...anything.

The 'ship in Geneva' idea would still work, since with no functional industrial base left, that would be the last chance to escape.