I might try just reloading the game having rebooting my PC or such, to see if it's that sort of bug, since it didn't give you the same impossible scenario. My issue was that despite using exactly those tactics I lose, brutally. Because when my troops attack, MY troops are usually the only ones taking damage. I assume there's an RNG for the defender to hurt the attacker, and if it crits you hit the attacker without taking damage yourself. And then for some reason in my game the pseudo-random broke.This is me playing the save you have sent me. My tactic is that I try to get all three of my units to attack first and gang on one enemy unit. The latter takes some planning, as you can see in the vid: at 1:58 I give my middle unit an Attack order and then I cancel it, move my unit to the side so the bottom unit will have a clear route to move and attack, all so I can attack the leftmost enemy with three of my guys in one round. Hope this helps!