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

Implement an HD option for automatic saving before and after each battle. This will also speed up the replay of moves in case of a disconnect.
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Actually, after implementing autosaving, the need for saving after disconnects suggests a ban on saving by the player in general. This applies to online play, of course. After all, nothing prevents the player from making a save beforehand, then checking something, and if something doesn't work out, disconnecting and thus returning to the initial state.
And if a loss is imminent, this could be recorded so that the player cannot manipulate the situation. After all, the opponent's presence in the battle can already be linked to a stopped, displayed timer.