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35 votes
Accepted

Running out of time before playing a forced move that would draw the game

In the final position where white's only legal move is Kxg8 leaving bare kings the position is a draw if white's flag falls before playing the move. The FIDE Laws of Chess are quite explicit: 6.9 ...
Brian Towers's user avatar
  • 98.6k
33 votes

Longest sequence of mutually forced moves

Assuming you allow promoted material (since you didn't say anything :-), this (on Page 13 of the PDF) is the (unfortunately, extremely unknown) finite record since ages. It shows the record for the ...
Hauke Reddmann's user avatar
27 votes
Accepted

Can anyone explain this sacrifice?

Black sacrifices the queen to deflect the bishop away from the a4-e8 diagonal; after 2. Bxc4 Rxh2, the threat of 3...Rh1# is winning. If Black attempts to skip 1...Qxc4+, playing 1...Rxh2?? then White ...
Allure's user avatar
  • 27.9k
23 votes

Is there a double-forced mate position?

Indeed, there are many possible positions in which all mates are forced on the first ply. Since you ask not for that, I shall provide examples with more than one move by both sides. Here is the known, ...
Rewan Demontay's user avatar
22 votes

Running out of time before playing a forced move that would draw the game

Draw by dead position Once Black plays 2...Qxg8 the game is a draw. At once, and whatever the clock situation. White doesn't even have to play 3.Kxg8 - it is irrelevant, but actually s/he shouldn't do ...
Evargalo's user avatar
  • 16.4k
20 votes
Accepted

What is the longest known sequence of forced moves leading to a checkmate for one side?

If you don't mind a bushel of promoted Queens, you can get 14 half-moves . . . [Title "14 forced half-moves to checkmate"] [Fen "3b3k/qqqqq3/rr4NK/7R/5N1Q/7Q/B6Q/7R b - - 0 0"] 1... Rxg6+ 2. Nxg6+ ...
Noam D. Elkies's user avatar
18 votes
Accepted

Is this position a forced win for Black after move 14?

The best move would have been 16. Rxe5, which entirely eliminates the mate threat, leaving white with a winning advantage. r6r/ppNk1p1p/3p2p1/2p1R3/2P3bq/3Q4/PP3PPP/R1B3K1 b - - 0 16 Here, if black ...
konsolas's user avatar
  • 3,196
14 votes
Accepted

What is the longest proven forced win (including 50 & 75 move rules)?

Otto Blathy is famous for his long mate problems. There are different records depending on whether you allow an illegal starting position, or promoted pieces, or minor duals in the solution, so your ...
Evargalo's user avatar
  • 16.4k
11 votes

A position in which checkmate is forced (obligatory)

I just remembered a class of chess problem; see item 267 of Tim Krabbé's Open Chess Diary (his whole site is highly recommended): [Title "White mates in 7, Noam Elkies, 2004."] [FEN "KBk5/P1P4p/2Pp3P/...
RemcoGerlich's user avatar
  • 28.2k
11 votes

What is the longest forced mate optimally played in documented competition?

I discovered a game from a few weeks ago that features a forced mate in 13 moves that was administered OTB. The game in question is Dubov-Svane, and the claim came from Agadmator’s analysis, for which ...
Rewan Demontay's user avatar
11 votes
Accepted

A special "dead" position

I am not sure if this is exactly what you are asking for, but here is a try. [FEN "8/8/8/2p1p1p1/2P1PkP1/4Q1RB/3PPpPp/3n1Kbr b - - 0 1"] [startflipped ""] 1... Nxe3+ 2.dxe3+ {2....
Evargalo's user avatar
  • 16.4k
10 votes
Accepted

Longest sequence of forcing moves?

The longest sequence I have created is 3648.5 moves long, abusing the 50-move rule to its fullest. Throughout the entire sequence, Black has only one legal move as stipulated. I can guarantee that ...
Rewan Demontay's user avatar
10 votes
Accepted

Do any unique proof games feature an en-passant capture?

There are plenty! There are currently 158 currently in the Die Schwalbe Chess Problem Database. For example, here is one with three consecutive en passants! [Title "Thierry Le Gleuher, R028c ...
Rewan Demontay's user avatar
8 votes

Is there a double-forced mate position?

Inspired by Thijs van Ede's answer, I've modified the pattern from Chess Diary #267 [FEN "K1k5/P1Pp4/3P4/1P6/1P6/8/5p2/8 w - - 0 1"] 1. b6 f1=B 2. b7# (2. b5 Bg2+ 3. b7+ Bxb7#) This ...
Hymns For Disco's user avatar
8 votes

Is there a double-forced mate position?

Rewan Demontay already has a great answer. However, I would also like to add this 'self-solving' chess problem from Tim Krabbé's Chess Diary #267. Here, all moves are forced and will lead to a ...
Thijs van Ede's user avatar
8 votes

An interesting positional chess riddle

[FEN "K3k2n/7n/rr1R3N/7n/8/8/4BQ2/4R3 w - - 0 1"] 1. Bxa6# Here is a much more simple situation where White only has only one legal move, which is a discovered checkmate.
yogazefish's user avatar
8 votes

Why is this position a forced mate?

I can't work out why black apparently has to play rdd6 at any point. If I were in his position, down by that amount of material, I would happily bounce my rook between d7 and d8 until the Queen takes ...
Chris's user avatar
  • 738
7 votes

A position in which checkmate is forced (obligatory)

The current record for most forced checkmates in a legal position with no promoted pieces is 29: [Title "Harold Holgate Cross, The Problemist FCS Apr 1936, 2251"] [StartFlipped "0"]...
Rosie F's user avatar
  • 6,425
7 votes

What is the chess position with biggest X, where no matter what legal move black/white does, a specific player will be mated at a max X moves later?

The longest known sequence is 22 plies long. [Title "Alexey Khanyan, Tim Krabbe's Website Diary Entry #267 2008, Mate In 11"] [FEN "4Q2Q/4r3/4n1n1/1bbK1krn/RR1RR1RR/2qn1R1n/4n1nN/Q3Q3 b ...
Rewan Demontay's user avatar
7 votes
Accepted

Longest sequence of unique legal moves for one player, always in check and ending in checkmate

Here is such a sequence of 627 moves. With some trickery utilizing captures, each position is indeed unique. Many thanks goes to @Noam D. Elkies for suggesting improvements. [Title "me, chess....
Rewan Demontay's user avatar
6 votes

What is the longest known sequence of forced moves leading to a checkmate for one side?

The longest known sequence, aka the record length, is 16 plies. I obtained this problem from the Die Schwalbe Chess Problem Database. It can be also be viewed on page 13 in a PDF of the original ...
Rewan Demontay's user avatar
6 votes

Longest forced sequence that ends with checkmate and every move is a check

Rosie F’s answer is a wonderful one. However, if you want it to be forced in terms of returning a check with a check, and having to make that move by the laws of chess, I have a different answer. The ...
Rewan Demontay's user avatar
6 votes

Longest forced sequence that ends with checkmate and every move is a check

The question asked in the title is different from the question asked in the body. If it is required that every best option is check, but it is allowed for the players to have non-checking ...
Rosie F's user avatar
  • 6,425
6 votes

What is the largest n such that discrete forced mate in one through mate in "n" exist?

Using wizardry to abuse the 50-move rule, I can make n equal 3053. White has a mate in one at any point and all of Black's moves are forced. Here, White has 47 pawn moves and 14 pieces to sacrifice. ...
Rewan Demontay's user avatar
5 votes
Accepted

What is White's motivation to give up the Queen?

What prevents 2. Qe2, which would save the White Queen? White's problem is the mating threats from the bishop battery and queen after Qc3. For instance: [Title "lichess puzzle 61506"] [FEN "rn2k3/...
Brian Towers's user avatar
  • 98.6k
5 votes

Is this position a forced win for Black after move 14?

15.g3 looks winning! 16.f4 is coming to win the Bishop on e5.
Ywapom's user avatar
  • 6,111
5 votes

Why is this position a forced mate?

Your position is so overwhelming you win almost regardless of what you do, but: 29.Qb7 Rd7 30.Qb8+ Rd8 31.Qc7 Rd7 32. Qxe5+ Kd8 (or 32...Re7 and 33. Qxe7#) 33. Qc8#. The 29. Qa7 line is the same, ...
Allure's user avatar
  • 27.9k
5 votes
Accepted

Minimal forced checkmate

Here's a reachable position (white to play) with five pieces and six legal moves, all of which checkmate. This was found with the assistance of computer search and some manual input from me. [Variant &...
Sisyphus's user avatar
  • 166
4 votes

Is this position a forced win for Black after move 14?

White could play 15. Bf4, covering h2 and attacking the Bishop on e5 which can't move due the pin in the e-file. But the probably stronger continuation is 15. g3 followed by 16. f4, winning the ...
Chris's user avatar
  • 181

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