Time for Some Mental Hygiene: It's the mental_floss Weekly Puzzle
Cat videos are cool and all, but the next time you’re in need of a mid-day pick-me-up, consider something slightly more stimulating: our weekly brain teaser, created by the late, great mathematician and puzzle master Martin Gardner. This week, it’s up to you to solve Lord Dunsany's chess problem.
LORD DUNSANY'S CHESS PROBLEM
Admirers of the Irish writer Lord Dunsany do not need to be told that he was fond of chess. (Surely his story "The Three Sailors' Gambit" is the funniest chess fantasy ever written.) Not generally known is the fact that he liked to invent bizarre chess problems which, like his fiction, combine humor and fantasy.
The problem depicted here was contributed by Dunsany to The Week-End Problems Book, compiled by Hubert Phillips. Its solution calls more for logical thought than skill at chess, although one does have to know the rules of the game. White is to play and mate in four moves. The position is one that could occur in actual play.
Once you've worked out a solution, scroll down to see if you're right.
From My Best Mathematical and Logic Puzzles, Martin Gardner, 1994, Dover Publications, Inc. Buy at Amazon.
The key to Lord Dunsany's chess problem is the fact that the black queen is not on a black square as she must be at the start of a game. This means the black king and queen have moved, and this could have happened only if some black pawns have moved. Pawns cannot move backward, so we are forced to conclude that the black pawns reached their present positions from the other side of the board! With this in mind, it is easy to discover that the white knight on the right has an easy mate in four moves.
White's first move is to jump his knight at the lower right corner of the board to the square just above his king. If black moves the upper left knight to the rook's file, white mates in two more moves. Black can, however, delay the mate one move by first moving his knight to the bishop's file instead of the rook's. White jumps his knight forward and right to the bishop's file, threatening mate on the next move. Black moves his knight forward to block the mate. White takes the knight with his queen, then mates with his knight on the fourth move.