Chess puzzle.
- Thread starter Ferocious
- Start date
Meh?
Don't play much. What prevents black from just moving back and forth. A rule against doing the same moves over and over?
Why did white have to keep going all that way for.
Don't play much. What prevents black from just moving back and forth. A rule against doing the same moves over and over?
Why did white have to keep going all that way for.
DrPizza
Administrator Elite Member Goat Whisperer
No.
The forced mate will occur in 271 moves from this position.
Pawn must have reached the other end....exchanged for Bishop. (Remember this is a puzzle.)
For all of you "why doesn't black do XYZQ?" people - that would reduce the number of moves, in some cases to only a few. 
Set it up on a board and you'll see it a lot easier.
- M4H
Set it up on a board and you'll see it a lot easier.
- M4H
I was taught that moving a king to one spot and back three times in succession was an automatic draw. not true?
Originally posted by: MercenaryForHire
For all of you "why doesn't black do XYZQ?" people - that would reduce the number of moves, in some cases to only a few.
Set it up on a board and you'll see it a lot easier.
- M4H
Exactly. If black where to do any other moves than back, forth (like 10+ times) then a pawn move, then black would lose much faster than 271 moves. Whites long triangulation pattern is the only way that black is forced into a mate while keeping the back/forth pattern. Basically, black found a good draw position, but white found a great triangulation to force mate.
You're thinking of three-repetition rule - and no. It has to be proven that the attacker has no plan to mate; and the other pieces cannot move.
Other ones - Insufficient material (that's a given) - 50-move-rule (Have never seen this one employed.)
- M4H
DrPizza
Administrator Elite Member Goat Whisperer
Understanding the solution:
First of all, notice that black cannot move the knight. It MUST protect the pawn on f6. Otherwise, bishop takes pawn, check, white advances pawn and gains a queen.
Also, obviously, black cannot advance that pawn without putting itself in check. That leaves black only able to move the pawn on f6, f7, h5, and h7. (11 wasting time moves) Because white moves the bishop to where it does on the first move, black cannot advance the pawn on d4 to d3, because, white pawn take black pawn, black pawn on c3 cannot move to c2 or bishop takes pawn. black has to move king back and forth, white pawn that took the black pawn moves forward, attacking the black knight - loss of black knight or moving black knight means white captures pawn on f3, check. If black king ever moved to c8, then white king moves to a6, protects pawn, gains queen.
Now, that long sequence of moves that you saw the white king make - it causes an odd number of moves to get back to its original spot because of the triangle at f1, f2, e1. Because of this, white has the opportunity to move to a6 while black is at a8 or c8 - again, protecting the pawn and gaining a queen. So, black has to move something else while the white king is at a5. Eventually, 100 and something moves later, black HAS to do something else; each of the choices leads to a forced mate.
Or, start trading pawn for pawn, gimme a queens, exchange of queens, etc.
Black's alternative is to move it's king away from that spot - white king moves to a6, then gains a queen in a move or two and game is virtually over.
White moves bishop to b1. Black cannot advance the pawn on d5 to d6 - because pxp, and the other pawn has no where to go - cannot gain a queen, bishop simply moves in front of that pawn on the next move
Black cannot move the knight - it must protect the pawn on f6. Otherwise, the bishop takes the pawn, check, and white can advance to gain a queen.
So, after a pxp exchange on d6, the white pawn cannot be attacked by the knight. (or game is virtually over)
Then, the white only needs to advance the pawn one space to attack the knight (and game is virtually over)
First of all, notice that black cannot move the knight. It MUST protect the pawn on f6. Otherwise, bishop takes pawn, check, white advances pawn and gains a queen.
Also, obviously, black cannot advance that pawn without putting itself in check. That leaves black only able to move the pawn on f6, f7, h5, and h7. (11 wasting time moves) Because white moves the bishop to where it does on the first move, black cannot advance the pawn on d4 to d3, because, white pawn take black pawn, black pawn on c3 cannot move to c2 or bishop takes pawn. black has to move king back and forth, white pawn that took the black pawn moves forward, attacking the black knight - loss of black knight or moving black knight means white captures pawn on f3, check. If black king ever moved to c8, then white king moves to a6, protects pawn, gains queen.
Now, that long sequence of moves that you saw the white king make - it causes an odd number of moves to get back to its original spot because of the triangle at f1, f2, e1. Because of this, white has the opportunity to move to a6 while black is at a8 or c8 - again, protecting the pawn and gaining a queen. So, black has to move something else while the white king is at a5. Eventually, 100 and something moves later, black HAS to do something else; each of the choices leads to a forced mate.
Or, start trading pawn for pawn, gimme a queens, exchange of queens, etc.
Black's alternative is to move it's king away from that spot - white king moves to a6, then gains a queen in a move or two and game is virtually over.
White moves bishop to b1. Black cannot advance the pawn on d5 to d6 - because pxp, and the other pawn has no where to go - cannot gain a queen, bishop simply moves in front of that pawn on the next move
Black cannot move the knight - it must protect the pawn on f6. Otherwise, the bishop takes the pawn, check, and white can advance to gain a queen.
So, after a pxp exchange on d6, the white pawn cannot be attacked by the knight. (or game is virtually over)
Then, the white only needs to advance the pawn one space to attack the knight (and game is virtually over)
AyashiKaibutsu
Diamond Member
- Jan 24, 2004
- 9,306
- 4
- 81
White got a pawn to the end of the board and replaced it with a bishop . . . what I don't understand is- why wouldn't you just get a queen instead?
edit: answering my own question. Because getting a queen instead of a bishop would shorten the number of "mate in 271 moves" . . . and the purpose of this exercise is to find the longest possible "mate in X moves" starting from a legal position.
When somebody says, "mate in X moves" . . . it means that the opponent is going to lose in at MOST X moves . . . but he can lose in less than X moves.
So in this example, where the chess board is set up the way it is, no matter what black does, he will lose in 271 moves or less. So the moves that black makes are the ones that will maximize the number of turns before he is checkmated.
Any other moves (than the ones given) will either quicken his death or do nothing.
Does that make sense?
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