Why does Fritz prefer underpromotion in this position? How can underpromotion to bishop evaluate so much higher than normal queen promotion?

Can this be a bug in the Fritz 14 chess engine?

Strange evaluation

1 Answer 1


It's because 1. exf8=Q+ Kxh7 2. Rxd7?? would be stalemate. I think it is a even a theoretical draw after 1. exf8=Q+ Kxh7 2. Qg7+. Therefore 1. exf8=B+! (with check!) is better, since white then can keep an extra piece and win easily.

[FEN "5r2/3qPbkB/8/7P/8/8/8/1K1R4 w - - 0 1"]

1. exf8=Q+ (1. exf8=B+!) Kxh7 2. Rxd7? (2. Qg7+)
  • 4
    Indeed, after 1.exf8Q+ Kxh7 2.Qg7+, it's a draw, according to the tablebases. It's the famous endgame R+p vs. B where white would be winning with a pawn on h2, h3 or h4, but not on h5!
    – Maxwell86
    Commented Jun 18, 2015 at 15:11
  • 4
    @Maxwell86 This endgame has also been discussed in an earlier question chess.stackexchange.com/questions/2801 Commented Jun 18, 2015 at 15:13
  • I don't want to seem dumb but what's wrong with kx(whatever is on f8)? I don't see how it varies either, because a queen can do all the bishop can!
    – Alec Teal
    Commented Jun 19, 2015 at 6:34
  • 2
    After 1.exf8=Q+ Kxf8 2.Rxd7 black is simply lost, that's what's wrong with it. Commented Jun 19, 2015 at 8:06

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.