Wizards is about an evil warlock digging up Nazi propaganda and Tanks form the remains of a civilisation destroyed in a nuclear war. He combines them with his magic to let his army of mutants and demons lead a successful Blitzkrieg campaign against the kingdom of Elves and Halflings who had forsaken technology in place of magic in order to avoid the fate that befell the previous pre-war civilisation.

I have not made any of this up, this is just the opening premise of Wizards by Ralph Bakshi. The entire film is like a good acid trip due to it's mix of rotoscoping and traditional animation techniques and I highly encourage everyone to give it a watch if they have the opportunity to do so.

The Wikipedia page

Full film is below:

From the movie Wizards