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Questions tagged [retrograde-analysis]

Retrograde analysis is the method of deducing information by working backwards from a given position or outcome. This information can be about past positions of the same game, or may contain forward content, such as optimal play.

In the realm of chess, retrograde analysis is prominent in the creation of endgame tablebases, as well as in composed chess problems (known as retros) in which the goal is to determine what move or sequence of moves immediately led up to a given position.

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How is this position possible in a normal game of chess?

A friend of mine gave me this problem. It goes like this. In a normal game of chess, the white player checks the black's king with a rook and a bishop as in the following image. 8/8/8/8/8/7k/8/3K1B1R b - - 0 1 Now the image seems a bit awkward. In…
Faiq Irfan
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A mysterious mate in one

Here's a question that's a little off the usual format, but problem questions like this have been done before and are on topic, so here we go! Question: Can you find the mysterious mate in one? The trick is not board rotation, removing a piece,…
Rewan Demontay
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Are there any illegal positions that are difficult to spot?

I have a question and I'm sorry if it sounds very uninformed, I'm not a professional chess player so my interest is mere curiosity. I was wondering if there are examples of illegal positions that require more than a superficial look at the…
seawalker
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Given a legal chess position, is there an algorithm that generates a series of moves that lead to it?

Given a FEN board position, is there an algorithm that can return a PGN move list that evaluates to it from the standard initial position?
2080
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Least number of moves to achieve a complete switchover of nonpawns in starting setup

[fen "RNBQKBNR/8/8/pppppppp/PPPPPPPP/8/8/rnbqkbnr w - - 0 1"] During a comp, my friend an I had a team kill and we decided to make this position(legally) before drawing. Then we continued to find more and more optimal ways of getting the position…
Ariana
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Can it be proven that 11. 0-0-0+ is legal in this position?

Because the chess site this was on takes its puzzles from real games and gives the move numbers, potential solvers knew that the following position was reached after exactly 10 moves by each player. [fen…
user2668
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Is the position in this trick question reachable?

I found this trick question on r/Anarchy chess: White to move, mate in two. [FEN "2R2RK/6PP/5P/3PN/P/1pQ3p/n1p1qbp/5brk w - - 0 1"] [StartFlipped "1"] The trick is that you're looking from Black's side, so the white pawn on the H file can promote…
SQB
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Prove that White is not allowed to castle here

A friend recently gave me the following weird chess problem to solve. I'm afraid that I'm struggling to see the key idea that would ultimately count as proof. From the position, intuitively speaking, it looks like White should be allowed to castle,…
user10376
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Is there fiction dealing with retrograde chess analysis?

I am interested in retrograde analysis problems, where the question usually is: 'What was the last move made?' or 'Where did the piece stand on the board before it fell from the table?' etc. Currently I know of only two occurrences of retrograde…
Ray
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Could a chess engine do retro analysis?

If I took a legal chess position, to what extent could an engine work out the previous moves? [in some other board games such as Othello such game reconstruction is done easily with an engine.]
Snack_Food_Termite
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Which methods can be used to prove that a position is illegal?

Given a board position, there are programs that try to find a series of legal moves that lead to it. Are there algorithms that can do the opposite - prove that the position is not reachable by a series of legal moves? Proof by exhaustion doesn't…
2080
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Can white win in this almost 20 year old puzzle?

It's White to move-can they force a win?. The left bottom is a1 as usual. [FEN "4k2r/6p1/p4pKb/p2N3p/p7/p5Q1/p1n5/qrn5 w - - 9 9"] Note for people who saw an earlier version: the position was edited (including a swap of the colors) for a more…
Albert Hendriks
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Beautiful retrograde analysis problem by Alexsey A. Troitsky

I saw this beautiful, subtle & accessible problem a couple of days ago, and wanted to share it with you folks. (It's by the ground-breaking endgame theorist who e.g. invented the "Troitsky line" in KNNvKP analysis.) [title "A.A.Troitsky - Bohemia…
Laska
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What is the result? (Rules + puzzle)

[EDITED to include followup - EDIT 2 to include definition of position] This is in part a genuine question on the FIDE Laws of Chess, and in part a small puzzle to solve. Suppose that during a long time control tournament game under FIDE rules the…
Remellion
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About how to compose retrograde analysis problems

Are there any books or articles devoted to composing retrograde analysis problems? It seems that you would need some techniques beyond ones for standard problems.
Christopher Heckman
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