10 years passed, still one of the best flash games out there!)
Dafuq else was I supposed to expect from The-Swain, I guess?
Update: I found the reason of the Infinite Attack Bug:
It's the Yellow Infantryman! Do not let them run away too far, or they'll "fall out from the map" into the limbo, where they'll live eternaly, prolonging the Attack.
To do so, constantly order your troops to Retereat by clicking at your base, before any of the Infantrymen escape, so the Yellow bitches will come closer to your attack range.
This must be an enemy AI problem.