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

Well, the player will still see the opponent's army at the beginning of their turn (except in the case where the opponent manages to hide, which, of course, makes sense), but the ability to plan based on real data during the opponent's turn, instead of adjusting plans during their own turn and wasting time (or planning two plans at once – for a large and a small army), seems more efficient in terms of time management.