Enemy AI Snaking

[Rokanon]

Hi, I think that's what it's called when enemy heroes try to sneak around whatever you're focusing on and attack your undefended structures and towns. I can think of a couple options here:

1. sacrifice numbers in my main hero army to sufficiently garrison each of my towns, or

2. reload autosaves from a turn back and just use advanced town portal to return to defend whatever's being snaked.

Are there any options better than this? There probably are. I don't claim to be very good at this game -- the last Heroes game I played was seriously 15 years ago.