5 ms·

"They're all legal. That is, reachable from the starting position in a valid game of chess." Help me out on the legality of some of these boards. I see excess

"They're all legal. That is, reachable from the starting position in a valid game of chess." Help me out on the legality of some of these boards. I see excess pieces on many boards (for example, 2 or more queens, 4 or more knights of one color). Are these considered legal by pawn conversion?

aliceryhl 5y ago
Pawn promotions are legal moves, yes.
syoc 5y ago
Yes. You do not need to choose a queen when the pawn reaches the opposite side.
- ctdonath 5y ago
  Were redundant choices culled? No point in tracking all variations of pawn > queen/rook/bishop when one includes the moves of the others.
  - tromp 5y ago
    There is sometimes a point when you need to avoid giving stalement, like in the famous Savedraa study [1] or the vastly more intricate Babson task [2]. [1] https://en.wikipedia.org/wiki/Saavedra_position https://en.wikipedia.org/wiki/Saavedra_position [2] https://en.wikipedia.org/wiki/Babson_task https://en.wikipedia.org/wiki/Babson_task
  - CrazyStat 5y ago
    Sometimes the queen having both rook and bishop moves is a liability. There are positions (real positions from real games, not merely hypothetical ones) where promoting to a queen results in immediate stalemate, while promoting to a rook wins the game. So those choices are not redundant.
- retrac 5y ago
  There are even times when this is the right move. Sometimes you can put them in check by promoting to a knight, for example, where a queen would not. Common in beginner puzzles.
  - Andrew_nenakhov 5y ago
    This is a very nice illustration of this, where a player had to turn off autoconversion to queen on the last seconds to win the game: https://youtu.be/HFG8pCInJKw https://youtu.be/HFG8pCInJKw
  - not1ofU 5y ago
    Your comment reminded me of this: https://www.youtube.com/watch?v=8wCJalNkTEI https://www.youtube.com/watch?v=8wCJalNkTEI Text: https://en.chessbase.com/post/solution-to-a-truly-remarkable-study https://en.chessbase.com/post/solution-to-a-truly-remarkable...
  - yoru-sulfur 5y ago
    Another situation where you would want to convert to something other than a queen is when doing so would result in a stalemate.
beckerdo 5y ago
So assuming all pawns of one color are converted, I guess 9 queens or 10 knights would be a legal, if unlikely, board setting, but 10 queens or 11 knights are not?
- phoe-krk 5y ago
  Yes. If you only have eight pawns, then you can only get eight extra pieces as a result of promotion.
seth00 5y ago
The 10 queens situation is obviously impossible, but so is having 2 white queens and black has all of his pawns on the starting squares. It's more difficult than you're thinking. If white has 6 dark squared bishops, they you know that he promoted at least 5 pawns on dark squares so one pawn must have taken a piece since it's promoting on a dark square instead of a white one. Not every board set-up will have enough missing pieces that 5 pawns can maneuver to get promoted on dark squares.

aliceryhl 5y ago

Pawn promotions are legal moves, yes.

syoc 5y ago

Yes. You do not need to choose a queen when the pawn reaches the opposite side.

ctdonath 5y ago
Were redundant choices culled? No point in tracking all variations of pawn > queen/rook/bishop when one includes the moves of the others.
- tromp 5y ago
  There is sometimes a point when you need to avoid giving stalement, like in the famous Savedraa study [1] or the vastly more intricate Babson task [2]. [1] https://en.wikipedia.org/wiki/Saavedra_position https://en.wikipedia.org/wiki/Saavedra_position [2] https://en.wikipedia.org/wiki/Babson_task https://en.wikipedia.org/wiki/Babson_task
- CrazyStat 5y ago
  Sometimes the queen having both rook and bishop moves is a liability. There are positions (real positions from real games, not merely hypothetical ones) where promoting to a queen results in immediate stalemate, while promoting to a rook wins the game. So those choices are not redundant.
retrac 5y ago
There are even times when this is the right move. Sometimes you can put them in check by promoting to a knight, for example, where a queen would not. Common in beginner puzzles.
- Andrew_nenakhov 5y ago
  This is a very nice illustration of this, where a player had to turn off autoconversion to queen on the last seconds to win the game: https://youtu.be/HFG8pCInJKw https://youtu.be/HFG8pCInJKw
- not1ofU 5y ago
  Your comment reminded me of this: https://www.youtube.com/watch?v=8wCJalNkTEI https://www.youtube.com/watch?v=8wCJalNkTEI Text: https://en.chessbase.com/post/solution-to-a-truly-remarkable-study https://en.chessbase.com/post/solution-to-a-truly-remarkable...
- yoru-sulfur 5y ago
  Another situation where you would want to convert to something other than a queen is when doing so would result in a stalemate.

beckerdo 5y ago

So assuming all pawns of one color are converted, I guess 9 queens or 10 knights would be a legal, if unlikely, board setting, but 10 queens or 11 knights are not?

phoe-krk 5y ago
Yes. If you only have eight pawns, then you can only get eight extra pieces as a result of promotion.

seth00 5y ago

The 10 queens situation is obviously impossible, but so is having 2 white queens and black has all of his pawns on the starting squares. It's more difficult than you're thinking. If white has 6 dark squared bishops, they you know that he promoted at least 5 pawns on dark squares so one pawn must have taken a piece since it's promoting on a dark square instead of a white one. Not every board set-up will have enough missing pieces that 5 pawns can maneuver to get promoted on dark squares.