Retrograde analysis

Chess is probably one of the most well-known board games in the world, with millions of players playing it around the world. There are two major divisions of chess: those that play chess as a game and those that play chess as a puzzle. Chess puzzles are further divided into two, tactical puzzles that are relevant for chess players and chess compositions that are rarely relevant for players, appealing for puzzle enthusiasts instead.

Something not interesting

Above: Mate in 3, a tactical puzzle taken from some chess game

Something interesting

Above: Mate in 4, composed by Vincente Maria N. Portilla in 1873

Something unique

Above: Helpmate in 8 (in helpmate, the two players cooperate to mate Black), composed by Z. Maslar in 1981

Chess compositions are divided into a large number of divisions (directmates and helpmates are two examples, shown above), but here I will talk about a quirky one, called retrograde analysis.

All you need to know are the rules of chess; you don't even need to know the strategies for playing chess, but you have to completely understand the rules. If you don't know the rules, turn back now and read that article until you completely understand it.

In retrograde analysis, you're not going forward in time...you're looking back in time.

MY COMPOSITION WHEE

Above: What was the last move? Composed by Ivan Koswara, 2014

You don't have to think about possible defenses like games and directmates; it's pure logic, much closer to a logic puzzle. Helpmates are similar.

Based on that sample puzzle above, do you find it interesting? Let me know!

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Remember to wrap math in `$` ... `$` or `\[` ... `\]` to ensure proper formatting.
`2 \times 3`	$2 \times 3$
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`\frac{2}{3}`	$\frac{2}{3}$
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`\sum_{i=1}^3`	$\sum_{i=1}^3$
`\sin \theta`	$\sin \theta$
`\boxed{123}`	$\boxed{123}$

Comments

axb8=R+

Franklyn Wang - 6 years, 11 months ago

Thank you for that thoughtful contribution to the discussion. :D

Finn Hulse - 6 years, 10 months ago

Wow, that's actually really cool!

Finn Hulse - 7 years, 1 month ago

I love all things about chess! Thanks for posting this.

I believe in the first problem, labeled "mate in 3", there is actually a mate in 2 moves for white.

Of course, I could be mistaken. Would someone like to look for the mate in 2 and respond?

Steven Perkins - 5 years, 5 months ago

Couldn't find it. Which move were you thinking about?

Vishnu Bhagyanath - 5 years, 2 months ago

The move I saw was: 1. Rxa8.

The threat is: 2. Qxa6#

If 1. .... Kxa8 2. Qxa6#

If the black knight moves, then: 2. Rb8#

I've probably missed something. Let me know if you see something I may have missed please?

Steven Perkins - 5 years, 2 months ago

@Steven Perkins – Hmm how about sac'ing the queen with 2.Qxd4 . Gives black king the escape square with Kxc6

@Vishnu Bhagyanath – I believe you're right!

Thanks for finding that for me.

While I was able to calculate that the last move played in the fourth problem above is aXb8=R, I am unable to determine which black piece was taken on b8. It could not have been the Queen or a Rook because then the white king would have been in check. But, that piece could either be a Knight or a Bishop. Which one was it?

Sourav Sahay - 5 years, 1 month ago

The White king can be in check; after all, because the White king is in check, White plays axb8=R+ to remove the check. The reason it can't be queen, rook, or bishop is that before that, Black has no last move.

Ivan Koswara - 5 years, 1 month ago

The answer to the first problem is 1.Nxa5+ Ka7 2.Qxa6+! Kxa6 3.Rxa8#

Freddie Hand - 4 years, 3 months ago

Math	Appears as
Remember to wrap math in `\(` ... `\)` or `\[` ... `\]` to ensure proper formatting.
`2 \times 3`	$2 \times 3$
`2^{34}`	$2^{34}$
`a_{i-1}`	$a_{i-1}$
`\frac{2}{3}`	$\frac{2}{3}$
`\sqrt{2}`	$\sqrt{2}$
`\sum_{i=1}^3`	$\sum_{i=1}^3$
`\sin \theta`	$\sin \theta$
`\boxed{123}`	$\boxed{123}$