Given three knights that can move to d2, one on b1, one on b3 and one on f3, how would you notate knight on b3 moves to d2? N3d2 is ambiguous, so would it be correct to write Nb3d2? Presume that a player has underpromoted to a third knight in this example.

1 Answer 1


Yes. You should disambiguate by adding either

  1. the file of departure (if they differ); or
  2. the rank of departure (if the files are the same but the ranks differ); or
  3. both the file and rank of departure (if neither alone is sufficient to identify the piece – which occurs only in rare cases where a player has three or more identical pieces able to reach the same square, as a result of one or more pawns having promoted).

Source: wikipedia.

This is an example of 3: neither rank or file alone is sufficient to identify the piece.

  • Note this possibility is amiss in the FIDE rules. As always, problem componists have found out :-) Still, the proposal here is sensible and obvious. Jul 12, 2021 at 17:38
  • @HaukeReddmann: The FIDE rules are surprisingly flexible on notation. For example, C.8 explicitly says that you can write both the rank and file of departure if you feel like it, even if there is no ambiguity at all! It also says that you can use either (1) or (2) at your preference in cases of ambiguity, although (1) is "preferred," whatever that is supposed to mean.
    – Kevin
    Jul 12, 2021 at 21:24

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