HoMM3 HD is a mod (add-on) for the game Heroes of Might and Magic 3.

I don't remember if I've mentioned this before: Quick Battle lasts for a maximum of 30 rounds; after 30 rounds, it ends, and the calculation begins as in a battle between two AIs (albeit a flawed one; the armies are taken as they were before the battle, but the mana spent during the battle is not returned). In general, this makes sense: the game shouldn't freeze because of a battle between two weak units, for example. In HD, as you can see, Quick Battle simply turns off after 30 rounds to avoid any unpleasant surprises.