Why isn't a draw considered? Simply because the attacker can often initiate such a stalemate when the opponent has a lot of slow units.
Otherwise, it seems like
the player has completely wasted all their magic, even running out of basic haste
and all this while having tons of units, in the middle of enemy territory, where they can still be attacked and harassed by weaker units.
I'm not even mentioning that such a situation can occur in a unit battle.
A stalemate in battle is equivalent to offering a draw in a game from the defending side.
The attacker has two options: agree to a draw or retreat (if this outcome is not satisfactory) and come back with a new army.
And if a draw is not beneficial to the defender, then they must retreat from the battle.
Both sides have a choice – agree to a draw or retreat and continue playing.
Unit battles have nothing to do with it.
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Nevertheless, regarding the first part of what Dirty said, the wording can be clarified.
I suggest the following draft of the final version:
Stalemate in Battle.
A stalemate in battle occurs when one of the sides avoids direct contact between units and does not inflict any damage on the opponent.
If the reason for the stalemate in battle is that the attacking player avoids contact, then the attacker is considered to have lost the battle and must retreat.
If the reason for the stalemate in battle is that the defending player avoids contact, then they must make a choice and either offer a draw in the game or retreat; upon receiving the draw offer, the attacker must either accept the draw or retreat.
A situation where a castle is stormed with a broken catapult is not considered a stalemate in battle – it is a loss for the attacker, and they must retreat.
In tournaments with a single-elimination system, after a draw, the players return to the situation that existed before the start of the game and begin the next generation with the same number of restarts.