I would like to ask if It is legal to under promote a pawn to opponents pieces? I mean like promoting white's pawn to a black's knight here will be a win. Here's the position for white; Ka5, b7 and Rc7 and for black; Ka7, Ra8.

[FEN "r7/kPR5/8/K7/8/8/8/8 w - - 0 1"]
[Title "Underpromotion"]

Hope to hear from you, many thanks.

  • 1
    In your above diagram, either if White plays bxa8 or b8, he can substitute the pawn only with white bishop, white knight, white rook or a white queen. He can not replace the pawn with black piece. – AlwaysLearningNewStuff Oct 30 '14 at 15:23

No, it is not.

FIDE Laws of chess, clause 3.7e:

When a pawn reaches the rank furthest from its starting position it must be exchanged as part of the same move on the same square for a new queen, rook, bishop or knight of the same colour.

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