Just to make sure we're playing this correctly:
When a unit retreat, it HAS to retreat through the shortest path towards it's HQ. If it can't, it's eliminated.
(This would, in effect, simulate simplified supply lines.)
Is this right?
I often use this rule as a way to wipe out some units that dare to come over to the CSA side. You can also do things like using a Retreat card (or 2) to force units off the board (also eliminated).