This Mate in 2 Puzzle Forced FIDE to Change the Rules of Chess 😱

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In this video lesson, GM Igor Smirnov will show you a funny chess puzzle that forced FIDE to change the rules of chess.

Tim Krabbé composed this puzzle in the year 1972, which was meant to be a mate in 3. It uses a loophole in the rules of the game that was present during those days. This eventually forced FIDE to change the rules. To be specific, it used the loophole called vertical castling.

Back then, the definition of castling was “It moves the king 2 squares towards the rook, while the rook takes the square that the king has crossed”. And because of this loophole, the castling rule was then updated such that the king and the rook are in the same rank (so that only horizontal castling is possible).

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► Chapters

00:00 Funny Chess Puzzle
00:08 Composition by Tim Krabbé in 1972
00:24 Can you solve this puzzle?
01:16 FIDE changed the rules after this
02:00 (Vertical) long castling?!
03:00 Loophole in chess rules
03:10 Can you find the mate in 2?

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93 Comments

  1. I didn't see the black bishop attacking the white rook. Oops

  2. White Kd6, black king have no square, if black play Rd3, then Bd5, checkmate andwhatever black play, Qb7 checkmate.

  3. In this puzzle, I can mate in one move.
    Whites :- Bxf7#

  4. So, has a vertical castle ever been played in an actual official game?

  5. Great little puzzle 1st move white RtoA4 black bh7xRb2 2nd move white QtoB4 mate! There R at least three other scenarios they all start with RtoA4 that end up with two moves mate.

  6. Great information I not know that. Thanks for the information. You are a great channel. I get very good chess content from this which helped me to Improve my chess.

  7. Why not mate on the move -mate in one. Play Ba2

  8. Id like to ask why tho? Is it so overpowered to do so?

  9. That is awesome. I could imagine Fischer making a big deal about it whether it happened to him or he performed it. Nice puzzel.

  10. This castling chance may appear 1 out of 100 million game.😁

  11. Is this right? Kd6?

    Kd6, now giving options for how black responds, Qb7 is the main threat. A counter check with Rd3+ leads to Bd5# or using Rg6+ leads to Be6#. The King running away to Kb4 leads to Kxc6#. I believe all other attempts to block/ignore white leads to Qb7#
    Someone Correct me if I'm wrong.

  12. But since the e4 square is attacked by the pawn on d5, wouldn't it be castling thru an attacked square and hence illegal?

  13. For puzzle: Kd6-Rd5+
    Bd5#
    Kd6-Rg6+
    Be6#
    Kd6-Kb6
    Bc2#

  14. awesome video, I have been playing chess for 30 years and have never seen such a concept!

  15. The puzzle is mate in one and has 4 solutions. Ba2#, Bd5#, Be6#, Bf7#. Am I missing something because everyone else is saying random stuff?

  16. I do not think the FIDE should have changed the rules. The circumstances required for this checkmate are extraordinary. It first requires a pawn promotion which is somewhat rare and it has to be on the King's file. Secondly, not already castling eitherside or forced to move the King this late into a game is shocking. It is one of the most unique checkmates I have ever seen. Changing the rules to avoid an almost unfathomable result is drastic and eliminates a very rare but cool way to checkmate an opponent.

  17. Answer to puzzle: 1st Rb2 to Ra1 2nd Ra3 to Ra5 mate!

  18. It seems like this castle should have been illegal anyway, because the new rook comes from a "promotion", meaning it is the really the pawn, and that pawn has obviously been moved.

  19. We have all explored all the variations and no one has found a forced 2 move mate. I think maybe Igor is pulling a joke on us. He`s probably laughing his ass off watching us trying to solve an impossible problem.

  20. I have some solutions to the puzzle depends on which piece black moves after Kd6. 1st Kd6-Kb4 2nd KxPc6 mate. 1st Kd6-Rd3 2nd Bd5mate. 1st Kd6-Kb6 2nd Bc2mate. 1st Kd6-BxRb1 2nd Qb7mate. 1st Kd6-Rg4 2nd Qb7mate Everything depends on which piece they move after U move Kd6. 1more 1st Kd6-Pc3to Pc2 2nd Qb7mate. There was more than 1 sollution to that puzzle. If I made a mistake let me know it's after 2am right now don't know if my brain is still working 🙃

  21. Great !!!!! Great !!!!!! What a Great Puzzele maker !!!! I salute him !!!!. In my chess life I don't expect it, this type of LEGALLY MATE !!!!

  22. GM Igor 2 moves is not possible because the black rook block the discover check. Key move
    Rook a4 rook g4
    Bishop C2+ rook b4
    Queen x rook +mate 😁

  23. First move is White Bishop to C2+, Black King must move to C4, then White Rook to A4, checkmate!

  24. This is why most speedrunners use an earlier version of chess, before wrongcastle was patched out.

  25. That is the cleverest chess puzzle I have ever seen since it took advantage of a loophole in the rules! Did anyone ever figure out the solution on their own?

  26. This idea was discovered much earlier, already. See https://de.wikipedia.org/wiki/Pam-Krabb%C3%A9-Rochade (not available in English)!

    Here's an anecdote regarding very long castling. I cannot remember where I have read it, though. In over the board blitz tournaments there is often not enough space for the player and they sometimes are sitting very close to each other.
    In such a tournament a player who had already lost one of his rooks used his neighbour's rooks to perform a VERY long castling. A few seconds later his neighbour wondered why one of his rooks had disappeared. Probably one of those "true" anecdotes…

  27. Why not after you promote to queen/rook, if the king goes g7, white Ke2, d4… RAg8#? Or after you promote to rook, if black goes …d4 reply with Re2 —- w/c guarantee the threatmate Rf8?

  28. Lame to change the rules of chess ! Why would they want to change it ! It's perfectly fine and cool LOL ! Disclaimer I am not a chess player ! Who knows maybe some king in ancient times actually used this trick ! 😉 =D

  29. Mate in 3 moves before FIDE's update about castling rule, with Pam–Krabbé castling rule.
    e7,

    – if gxf3, e8=Q+ or e8=R+, Kd3, O-O-O#;

    – if d4,
    e8=Q+, Kd3, Qe2# or O-O-O#,
    or
    e8=R+, Kd3, O-O-O#;

    – if Kxf3, e8=R,
    if Kg2, O-O-O-O-O-O#/Vertical Castle (Ke3 and Re2)#,
    if d4, O-O#;

    – if Kd3,
    e8=R,
    if Kc2, O-O-O-O-O-O#/Vertical Castle (Ke3 and Re2)#,
    if d4 or gxf3, O-O-O#,
    or
    e8=Q,
    if Kc2, Qe2#,
    if d4, Qe4# or Qe2# or O-O-O#,
    if gxf3, O-O-O#.

    Mate in 4 moves after FIDE's update about castling rule, without Pam–Krabbé castling rule.
    e7,

    – if gxf3, e8=Q+ or e8=R+, Kd3, O-O-O#;

    – if d4,
    e8=Q+, Kd3, Qe2# or O-O-O#,
    or
    e8=R+, Kd3, O-O-O#;

    – if Kxf3, e8=Q,
    if Kg2, Qe2+, Kxh1, Kd2# or O-O-O#,
    if d4, Qe2# or O-O#;

    – if Kd3,
    e8=Q,
    if Kc2, Qe2#,
    if d4, Qe4# or Qe2# or O-O-O#,
    if gxf3, O-O-O#.

  30. Last puzzle:
    Kd6,
    – if Rd3+, Bd5#;
    – if Rg6+, Be6#;
    – if Kb4, Kxc6#;
    – if Kb6, Bc2#;
    – if f5, Ba2# or Bd5# or Be6# or Bf7# or Bg8# or Qb7#;
    – if Bg8, Ba2# or Bd5# or Be6# or Bxf7# or Qb7#;
    – if any other black legal move, Qb7#.

  31. Ba2 is even mate in 1 in the second puzzle.

  32. This patch sucked I want the devs to add this back

  33. wait, is this puzzle from a real game? It's unclear if they're talking about fischer and spassky's game or just a specifically made puzzle for vertical castling

  34. Never in my life I have heard of this strange castling demonstrated in this video.

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