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Topic: Black's Last Move? (Read 1542 times) |
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ThudnBlunder
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What was Black's last move?
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wowbagger
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Re: Black's Last Move?
« Reply #1 on: Sep 4th, 2003, 3:40am » |
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Let me ask a question to clarify the rules of your reconstruction problems:
You're looking for a unique solution, right? I mean one where the moves are forced. Otherwise, -1. ... Kg1-h2 would be too obvious a possibility, but that wouldn't be forced as Black could also have captured on g2.
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ThudnBlunder
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Re: Black's Last Move?
« Reply #2 on: Sep 4th, 2003, 7:53am » |
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Wowbagger, GIVEN the above board position, there is only ONE possible last move by Black.
That's NOT the same as saying that the move was forced.
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| « Last Edit: Sep 4th, 2003, 8:01am by ThudnBlunder » |
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Sir Col
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Re: Black's Last Move?
« Reply #3 on: Sep 4th, 2003, 8:27am » |
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I don't know how you use the chess notation, but... after white castled with the king, the black king was in check, so it was forced to move from G1 to H2. But, as wowbagger said, I don't know why the king didn't capture the pawn?
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| « Last Edit: Sep 4th, 2003, 8:30am by Sir Col » |
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wowbagger
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Re: Black's Last Move?
« Reply #4 on: Sep 4th, 2003, 8:29am » |
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on Sep 4th, 2003, 7:53am, THUDandBLUNDER wrote:| Wowbagger, GIVEN the above board position, there is only ONE possible last move by Black. |
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I dont think so. How about -2. ... Qh4xQd1+ -1. Rg1xd1 with Black to move - you didn't say the last move played was a Black move!
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wowbagger
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Re: Black's Last Move?
« Reply #5 on: Sep 4th, 2003, 8:32am » |
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on Sep 4th, 2003, 8:27am, Sir Col wrote:| I don't know how you use the chess notation |
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Castling to the Kingside is 0-0, to the Queenside (Queen's side?), 0-0-0.
Quote:| [the black king] was forced to move from G1 to H2. |
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As you say yourself, he could have captured on g2, so the move wasn't forced.
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| « Last Edit: Sep 4th, 2003, 8:35am by wowbagger » |
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ThudnBlunder
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Re: Black's Last Move?
« Reply #6 on: Sep 4th, 2003, 8:34am » |
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Quote:| you didn't say the last move played was a Black move! |
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OK, what move did Black JUST play??
Given the above board position, his last move was forced.
Given the previous board position, his next move is NOT forced.
I don't think many solvers here have the hang of these retro puzzles yet.
They are not about 'best' moves, but about possible moves.
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| « Last Edit: Sep 4th, 2003, 11:05am by ThudnBlunder » |
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wowbagger
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Re: Black's Last Move?
« Reply #7 on: Sep 4th, 2003, 8:39am » |
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on Sep 4th, 2003, 8:34am, THUDandBLUNDER wrote:
OK, what move did Black JUST play?? |
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What are you aiming at?
The original question was " What was Black's last move?".
My answer: I don't know. There are too many possibilities, becase I don't know whether it's White to move now, which would imply that the immediately preceding move would have been made by Black... ...and would have been Kg1-h2
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| « Last Edit: Sep 4th, 2003, 8:40am by wowbagger » |
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ThudnBlunder
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Re: Black's Last Move?
« Reply #8 on: Sep 4th, 2003, 8:41am » |
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BLACK played last.
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ThudnBlunder
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Re: Black's Last Move?
« Reply #9 on: Sep 4th, 2003, 8:41am » |
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The last move was by BLACK.
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wowbagger
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Re: Black's Last Move?
« Reply #10 on: Sep 4th, 2003, 8:45am » |
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on Sep 4th, 2003, 8:34am, THUDandBLUNDER wrote:| I don't think many solvers here have the hang of these retro puzzles yet. |
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That's definitely true! 
Maybe you should expound on the rules to this sort of puzzle in a separate thread in the FAQ section. You could then link to this thread to help beginners.
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| « Last Edit: Sep 4th, 2003, 8:47am by wowbagger » |
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ThudnBlunder
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Re: Black's Last Move?
« Reply #11 on: Sep 4th, 2003, 8:54am » |
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Quote:| Maybe you should expound on the rules to this sort of puzzle in a separate thread in the FAQ section that you could link to. |
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Retrograde Analysis is a genre of chess problems where the legality of the position is a key element.
A position is legal if it can be reached through a legal chess game (no matter how weird).
Retros may ask (for example) for a mate in two, but the main content is in analysing the history of the position.
This is essentially a matter of logical reasoning.
For complete beginners, the Sherlock Holmes book by Raymond Smullyan is a good start.
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| « Last Edit: Sep 4th, 2003, 9:20am by ThudnBlunder » |
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wowbagger
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Re: Black's Last Move?
« Reply #12 on: Sep 4th, 2003, 8:57am » |
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on Sep 4th, 2003, 8:41am, THUDandBLUNDER wrote:
on Sep 4th, 2003, 8:41am, THUDandBLUNDER wrote:| The last move was by BLACK. |
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You think I would have found only one of these formulations not clear-cut enough? 
So the correct answer is Kg1-h2?
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wowbagger
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Re: Black's Last Move?
« Reply #13 on: Sep 4th, 2003, 9:04am » |
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on Sep 4th, 2003, 8:54am, THUDandBLUNDER wrote:| For complete beginners, the Sherlock Holmes book by Raymond Smullyan is a very good start. |
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Thanks for the recommendation, I put it on my list of books to buy.
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Kitty
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Re: Black's Last Move?
« Reply #14 on: Sep 4th, 2003, 9:05am » |
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Yeah but would not the tower have eaten it, i mean look at where the tower is now, how did it get there? If you get what i'm saying 
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ThudnBlunder
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Re: Black's Last Move?
« Reply #15 on: Sep 4th, 2003, 9:05am » |
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Quote:| You think I would have found only one of these formulations not clear-cut enough? |
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Why did I post two? Because I couldn't think of anymore.
Quote:| So the correct answer is Kg1-h2? |
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No. (Hehe.) There is a good reason why not.
Consider what White must have played before that move (Kg1-h2), and study the position.
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| « Last Edit: Sep 4th, 2003, 11:04am by ThudnBlunder » |
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ThudnBlunder
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Re: Black's Last Move?
« Reply #16 on: Sep 4th, 2003, 9:10am » |
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Quote:| Yeah but would not the tower have eaten it, i mean look at where the tower is now, how did it get there? |
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Kitty, there exists a 'double move' in chess called 'castling'. 
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| « Last Edit: Sep 4th, 2003, 9:19am by ThudnBlunder » |
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Kitty
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Re: Black's Last Move?
« Reply #17 on: Sep 4th, 2003, 9:24am » |
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Fine, I don't play chess, i just guessing. 
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wowbagger
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Re: Black's Last Move?
« Reply #18 on: Sep 4th, 2003, 9:52am » |
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on Sep 4th, 2003, 9:05am, THUDandBLUNDER wrote:| Consider what White must have played before that move (Kg1-h2), and study the position. |
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Okay, I think I'm starting to really appreciate this one.
Here's what I have arrived at by now, using my retro-notation - if there is some other, standard way, let me know:
-1. ... Kg1-h2
-2. 0-0-0 Kh2-g1 (forced)
The only White pieces allowed to have moved further back in the past are the Knight and the former f- or h-Pawn (otherwise White would have lost the right to castle).
I claim that this is not a legal position, as the Black King could not have arrived at h2: Ke1 and Pg2 block all squares but g3. This last one was controlled by the f- or h-Pawn, unless the capture on g3 took place before the Black King got through. In this case, however, the Black King is also blocked from arriving at h2 (without contradicting the final position).
Boy, this is really cumbersome to explain! - Or is it just me?
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| « Last Edit: Sep 4th, 2003, 9:54am by wowbagger » |
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ThudnBlunder
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Re: Black's Last Move?
« Reply #19 on: Sep 4th, 2003, 10:03am » |
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Yes, wowbagger, you are on the right track!
Your conclusion?
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| « Last Edit: Sep 5th, 2003, 6:48am by ThudnBlunder » |
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wowbagger
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Re: Black's Last Move?
« Reply #20 on: Sep 4th, 2003, 10:12am » |
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on Sep 4th, 2003, 10:03am, THUDandBLUNDER wrote:
That the position isn't legal?
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ThudnBlunder
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Re: Black's Last Move?
« Reply #21 on: Sep 4th, 2003, 10:29am » |
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Quote:| That the position isn't legal? |
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Now that wouldn't be much of a chess puzzle, would it?
The above board position is a legal one and Black has JUST played a legal move.
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| « Last Edit: Sep 4th, 2003, 8:14pm by ThudnBlunder » |
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I assume his last move was g1 to h2. But the only way for the black king to get to g1 is if the castling move occurred early. Then there must have been a white piece between him and the rook. It must have been a knight that moved to h2, and the black king knocked it off on his final turn.
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Sorry, my solution doesn't work. It doesn't leave black with any valid move on its turn right before the knight moved to h2. Back to the drawing board.
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Let's say there was a bishop on e1 when the black king moved in (d3,e2,f1,g1). Bf2...Kh2.
Be3 where it was knocked off by some black piece. Nxe3
Black moved its only other piece somewhere. white Nf1. Black moves that other piece to c1, where it's knocked off by the white king. Then black Kg1, Nh2, Kxg2.
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