Answers.Body: <p>According to
  <a href="https://madchess.wordpress.com/2012/06/17/shortest-legal-en-passant-mates/" rel="noreferrer">this page</a>
  the shortest known mate by <em>en passant</em> capture is in 5.5 moves
  (that is, White mates on move 6), and was published by Benko in
  <em>Chess Live &amp; Review</em> in 1976:</p>
  
  <pre><code>[Title "Pal Benko's 5.5 move e.p. helpmate"]
  [Fen "rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR w - - 0 0"] 
  
  1. e4 e5 2. Qh5 Nc6 3. g4 d6 4. g5 Kd7 5. Bh3+ f5 6. gxf6#
  </code></pre>
  
Answers.ContentLicense: CC BY-SA 4.0
Answers.CreationDate: 2018-05-02T01:33:50.997Z
Answers.Text: . . . and there are several more recent 5.5 movers tied with it.
Answers.UserDisplayName: Noam D. Elkies
Answers.ContentLicense: CC BY-SA 4.0
Answers.CreationDate: 2018-05-02T08:32:21.057Z
Answers.Text: this only answers half of the question, how many moves does it take to checkmate white?
Answers.UserDisplayName: micsthepick
Answers.ContentLicense: CC BY-SA 4.0
Answers.CreationDate: 2018-05-02T08:45:50.797Z
Answers.Text: @micsthepick : It can't be more than 6.0 (black checkmates on move 6).  `1. a3 ...` and then the above sequence with white and black swapped would do it.
Answers.UserDisplayName: Martin Bonner supports Monica
Answers.ContentLicense: CC BY-SA 4.0
Answers.CreationDate: 2018-05-04T11:39:50.803Z
Answers.Text: just to clarify, the original question was meant to ask for a checkmate on both sides. It may not have been clear through the use of “either”, so I changed it to say each.
Answers.UserDisplayName: micsthepick
Answers.ContentLicense: CC BY-SA 4.0
Answers.CreationDate: 2018-05-02T01:07:07.353Z
Answers.LastActivityDate: 2018-05-02T01:07:07.353Z
Answers.UserDisplayName: Noam D. Elkies
Answers.Body: <p>Thanks for the subject! A natural, fun extension of the question is to ask what is the shortest <strong>Unique Proof Game</strong> ending in e.p. checkmate. The idea with one of these is you are given just the end state diagram, and the total number of moves, and you must figure out the unique game leading to that point.</p>
  
  <p>I think the current record holder is the following:</p>
  
  <pre><code>
  [title "Gerd Wilts & Norbert Geissler - RML - 05/1996"]
  [fen ""]
  [startply "14"]  
  
  1. f4 e5 2. Kf2 Qh4+ 3. Kf3 Qf2+ 4. Kg4 h5+ 5. Kh3 h4 6. e4 d5+ 7. g4 hxg3ep# *
  </code></pre>   
  
  <p>Position after Black's 7th move.  </p>
  
  <p>I honestly don't know if this is the best possible: maybe there is another position with a shorter unique proof game.</p>
  
Answers.ContentLicense: CC BY-SA 4.0
Answers.CreationDate: 2018-05-04T13:53:44.007Z
Answers.Text: Is the same diagram without Pf4 also a unique proof game ? 1.e3 e5 2.Ke2 Qh4 3.Kf3 Qxf2 4.Kg4 h5 5.Kh3 h4 6.e4 d5 7.g4 hg3ep# ?
Answers.UserDisplayName: Evargalo
Answers.ContentLicense: CC BY-SA 4.0
Answers.CreationDate: 2018-05-04T15:05:46.870Z
Answers.Text: @Evargalo no your suggestion isn't unique. Francois Labelle's Jacobi program at http://wismuth.com/jacobi/ identifies 25 routes to the final position.
Answers.UserDisplayName: Laska
Answers.ContentLicense: CC BY-SA 4.0
Answers.CreationDate: 2024-06-12T05:17:06.443Z
Answers.Text: nice double check checkmate
Answers.UserDisplayName: Lucenaposition
Answers.ContentLicense: CC BY-SA 4.0
Answers.CreationDate: 2018-05-03T05:21:28.630Z
Answers.LastActivityDate: 2018-05-03T05:21:28.630Z
Answers.UserDisplayName: Laska
Answers.Body: <p>There are four kinds of en passant checkmates.</p>
  <ol>
  <li>The pawn moves, checking the king itself.</li>
  <li>The pawn moves, checking the king, while also allowing another piece to check as well. This is a double check.</li>
  <li>The pawn moves, not checking the king, as to allow another piece to check the king. This is a discovered check.</li>
  <li>The pawn moves, not checking the king itself, as to allow two other pieces to check the king. This is a double discovered check.</li>
  </ol>
  <p>Here are the fastest possible games for each category.
  Reversing each game, adding on a ply, provides for Black's fastest mates. These are sourced from the same Lichess forum linked in the accepted answer.</p>
  <pre><code>[Title &quot;Type #1&quot;]
  [FEN &quot;&quot;]
  
  1. e4 f5 2. exf5 Kf7 3. Qg4 h6 4. b3 Qe8 5. Bb2 g5 6. fxg6#
  </code></pre>
  <hr />
  <pre><code>[Title &quot;Type #2&quot;]
  [FEN &quot;&quot;]
  
  1. e4 d5 2. d4 dxe4 3. d5 Kd7 4. Bc4 Nc6 5. Bg5 Qe8 6. h3 e5 7. dxe6#
  </code></pre>
  <hr />
  <pre><code>[Title &quot;Type #3&quot;]
  [FEN &quot;&quot;]
  
  1. e4 e5 2. g4 Nc6 3. g5 d6 4. Qh5 Kd7 5. Bh3+ f5 6. gxf6#
  </code></pre>
  <hr />
  <pre><code>[Title &quot;Type #4&quot;]
  [FEN &quot;&quot;]
  
  1. c3 f5 2. h4 Kf7 3. Qb3+ Kg6 4. Qf7+ Kh6 5. h5 a6 6. d4+ g5 7. hxg6#
  </code></pre>
  
Answers.ContentLicense: CC BY-SA 4.0
Answers.CreationDate: 2019-03-31T14:52:24.127Z
Answers.LastActivityDate: 2021-06-09T23:31:00.977Z
Answers.LastEditDate: 2021-06-09T23:31:00.977Z
Answers.UserDisplayName: Rewan Demontay
Answers.Body: <p>The same question has also been <a href="https://lichess.org/forum/general-chess-discussion/competition-create-the-shortest-game-with-ep-and-mate-pxp-ep-?page=1" rel="noreferrer">discussed and answered in the lichess forum</a>, and as mentioned by others already, the answer is <strong>11 half-moves for white</strong> and <strong>12 half-moves for black</strong>. You might find some interesting examples and additional info there. Not knowing that this problem had already been solved before, I did a brute-force proof back then (see <a href="https://lichess.org/forum/general-chess-discussion/competition-create-the-shortest-game-with-ep-and-mate-pxp-ep-?page=2#13" rel="noreferrer">my post in the aforementioned thread</a>), since that is feasible for 10-12 ply, i.e., disproving the existence of a solution up to 10 ply by an exhaustive search and finding solutions with 11 and 12 ply, respectively.</p>
  
  <p>Here are displays for said games.</p>
  
  <pre><code>[FEN ""]
  
  1. e4 e6 2. e5 g5 3. Nc3 Nh6 4. Qh5 Ke7 5. Ne4 f5 6. exf6#
  </code></pre>
  
  <hr>
  
  <pre><code>[FEN ""]
  
  1. f3 e5 2. Kf2 Qf6 3. Kg3 h5 4. h3 h4+ 5. Kh2 Qxf3 6. g4 hxg3#
  </code></pre>
  
Answers.ContentLicense: CC BY-SA 4.0
Answers.CreationDate: 2018-05-04T15:09:12.847Z
Answers.Text: @FabianFichter thanks for this. Was your analysis of 11 & 12 ply also exhaustive? If so, that would indicate whether there are any unique proof games of that length.
Answers.UserDisplayName: Laska
Answers.ContentLicense: CC BY-SA 4.0
Answers.CreationDate: 2018-05-04T15:41:21.940Z
Answers.Text: @Laska I think for 11 ply it was exhaustive and for 12 ply it wasn't, but I not not clearly remember. I just took Stockfish's perft implementation and printed/counted all final positions that fulfilled the respective requirement (e.g., I did the same for shortest checkmate by a king move), so it was quite simple, but I can not find the code or the results any more. I think I only added one or two conditions to return early if no en passant capture was possible within the remaining search depth in order to speed it up a little bit, since perft 11/12 already takes quite a while.
Answers.UserDisplayName: Fabian Fichter
Answers.ContentLicense: CC BY-SA 4.0
Answers.CreationDate: 2020-03-08T06:05:16.473Z
Answers.Text: Wow. Now, how about *stalemate* by an e.p. capture? Has that been solved too?
Answers.UserDisplayName: bof
Answers.ContentLicense: CC BY-SA 4.0
Answers.CreationDate: 2020-03-09T19:08:59.193Z
Answers.Text: The shortest known stalemate https://en.wikipedia.org/wiki/List_of_world_records_in_chess#Shortest_stalemate has 19 half-moves, so finding the shortest stalemate by en passant using brute force does not seem feasible.
Answers.UserDisplayName: Fabian Fichter
Answers.ContentLicense: CC BY-SA 4.0
Answers.CreationDate: 2018-05-04T11:14:02.707Z
Answers.LastActivityDate: 2020-01-15T15:02:04.403Z
Answers.LastEditDate: 2020-01-15T15:02:04.403Z
Answers.UserDisplayName: Fabian Fichter
Body: <p>En passant is somewhat of a rare move in chess. Checkmating by en passant, however, is an even rarer occurrence. But suppose both sides had the same goal to help cause a checkmate to their opponent via en passant.</p>
  <p>What is the minimum amount of moves needed by both White and Black to give checkmate by en passant?</p>
  
Comments.ContentLicense: CC BY-SA 4.0
Comments.CreationDate: 2021-04-08T17:05:30.650Z
Comments.Text: Now before someone asks (like me) "And by castling? And...And...", here is a collection answering a lot of related questions: http://www.mayhematics.com/p/syntheticgames.pdf
Comments.UserDisplayName: Hauke Reddmann
Tags: <problems><checkmate><records><en-passant>
Title: Fastest possible checkmate by en passant
ThreadText: # Fastest possible checkmate by en passant
  
  (Asked by: username_0 on 2018-05-01)
  
  En passant is somewhat of a rare move in chess. Checkmating by en passant, however, is an even rarer occurrence. But suppose both sides had the same goal to help cause a checkmate to their opponent via en passant.
  
  What is the minimum amount of moves needed by both White and Black to give checkmate by en passant?
  
  **Tags:** problems, checkmate, records, en-passant
  
  > **Comments:**
  > **username_1**: Now before someone asks (like me) "And by castling? And...And...", here is a collection answering a lot of related questions: http://www.mayhematics.com/p/syntheticgames.pdf  
  
  ---
  
  ## 4 answers
  
  ### Answer by username_8 on 2018-05-04. Score: 15 | Accepted answer
  
  The same question has also been [discussed and answered in the lichess forum](https://lichess.org/forum/general-chess-discussion/competition-create-the-shortest-game-with-ep-and-mate-pxp-ep-?page=1), and as mentioned by others already, the answer is **11 half-moves for white** and **12 half-moves for black**. You might find some interesting examples and additional info there. Not knowing that this problem had already been solved before, I did a brute-force proof back then (see [my post in the aforementioned thread](https://lichess.org/forum/general-chess-discussion/competition-create-the-shortest-game-with-ep-and-mate-pxp-ep-?page=2#13)), since that is feasible for 10-12 ply, i.e., disproving the existence of a solution up to 10 ply by an exhaustive search and finding solutions with 11 and 12 ply, respectively.
  
  Here are displays for said games.
  
  ```
  [FEN ""]
  
  1. e4 e6 2. e5 g5 3. Nc3 Nh6 4. Qh5 Ke7 5. Ne4 f5 6. exf6#
  
  ```
  
  ---
  
  ```
  [FEN ""]
  
  1. f3 e5 2. Kf2 Qf6 3. Kg3 h5 4. h3 h4+ 5. Kh2 Qxf3 6. g4 hxg3#
  
  ```
  
  > **Comments:**
  > **username_4**: @username_8 thanks for this. Was your analysis of 11 & 12 ply also exhaustive? If so, that would indicate whether there are any unique proof games of that length.  
  > **username_8**: @username_4 I think for 11 ply it was exhaustive and for 12 ply it wasn't, but I not not clearly remember. I just took Stockfish's perft implementation and printed/counted all final positions that fulfilled the respective requirement (e.g., I did the same for shortest checkmate by a king move), so it was quite simple, but I can not find the code or the results any more. I think I only added one or two conditions to return early if no en passant capture was possible within the remaining search depth in order to speed it up a little bit, since perft 11/12 already takes quite a while.  
  > **username_9**: Wow. Now, how about *stalemate* by an e.p. capture? Has that been solved too?  
  > **username_8**: The shortest known stalemate https://en.wikipedia.org/wiki/List_of_world_records_in_chess#Shortest_stalemate has 19 half-moves, so finding the shortest stalemate by en passant using brute force does not seem feasible.  
  
  ---
  
  ### Answer by username_2 on 2018-05-02. Score: 16
  
  According to
  [this page](https://madchess.wordpress.com/2012/06/17/shortest-legal-en-passant-mates/)
  the shortest known mate by *en passant* capture is in 5.5 moves
  (that is, White mates on move 6), and was published by Benko in
  *Chess Live & Review* in 1976:
  
  ```
  [Title "Pal Benko's 5.5 move e.p. helpmate"]
  [Fen "rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR w - - 0 0"] 
  
  1. e4 e5 2. Qh5 Nc6 3. g4 d6 4. g5 Kd7 5. Bh3+ f5 6. gxf6#
  
  ```
  
  > **Comments:**
  > **username_2**: . . . and there are several more recent 5.5 movers tied with it.  
  > **username_0**: this only answers half of the question, how many moves does it take to checkmate white?  
  > **username_3**: @username_0 : It can't be more than 6.0 (black checkmates on move 6).  `1. a3 ...` and then the above sequence with white and black swapped would do it.  
  > **username_0**: just to clarify, the original question was meant to ask for a checkmate on both sides. It may not have been clear through the use of “either”, so I changed it to say each.  
  
  ---
  
  ### Answer by username_4 on 2018-05-03. Score: 7
  
  Thanks for the subject! A natural, fun extension of the question is to ask what is the shortest **Unique Proof Game** ending in e.p. checkmate. The idea with one of these is you are given just the end state diagram, and the total number of moves, and you must figure out the unique game leading to that point.
  
  I think the current record holder is the following:
  
  ```
  
  [title "Gerd Wilts & Norbert Geissler - RML - 05/1996"]
  [fen ""]
  [startply "14"]  
  
  1. f4 e5 2. Kf2 Qh4+ 3. Kf3 Qf2+ 4. Kg4 h5+ 5. Kh3 h4 6. e4 d5+ 7. g4 hxg3ep# *
  
  ```
  
  Position after Black's 7th move.
  
  I honestly don't know if this is the best possible: maybe there is another position with a shorter unique proof game.
  
  > **Comments:**
  > **username_5**: Is the same diagram without Pf4 also a unique proof game ? 1.e3 e5 2.Ke2 Qh4 3.Kf3 Qxf2 4.Kg4 h5 5.Kh3 h4 6.e4 d5 7.g4 hg3ep# ?  
  > **username_4**: @username_5 no your suggestion isn't unique. Francois Labelle's Jacobi program at http://wismuth.com/jacobi/ identifies 25 routes to the final position.  
  > **username_6**: nice double check checkmate  
  
  ---
  
  ### Answer by username_7 on 2019-03-31. Score: 1
  
  There are four kinds of en passant checkmates.
  
  1. The pawn moves, checking the king itself.
  2. The pawn moves, checking the king, while also allowing another piece to check as well. This is a double check.
  3. The pawn moves, not checking the king, as to allow another piece to check the king. This is a discovered check.
  4. The pawn moves, not checking the king itself, as to allow two other pieces to check the king. This is a double discovered check.
  
  Here are the fastest possible games for each category.
  Reversing each game, adding on a ply, provides for Black's fastest mates. These are sourced from the same Lichess forum linked in the accepted answer.
  
  ```
  [Title "Type #1"]
  [FEN ""]
  
  1. e4 f5 2. exf5 Kf7 3. Qg4 h6 4. b3 Qe8 5. Bb2 g5 6. fxg6#
  
  ```
  
  ---
  
  ```
  [Title "Type #2"]
  [FEN ""]
  
  1. e4 d5 2. d4 dxe4 3. d5 Kd7 4. Bc4 Nc6 5. Bg5 Qe8 6. h3 e5 7. dxe6#
  
  ```
  
  ---
  
  ```
  [Title "Type #3"]
  [FEN ""]
  
  1. e4 e5 2. g4 Nc6 3. g5 d6 4. Qh5 Kd7 5. Bh3+ f5 6. gxf6#
  
  ```
  
  ---
  
  ```
  [Title "Type #4"]
  [FEN ""]
  
  1. c3 f5 2. h4 Kf7 3. Qb3+ Kg6 4. Qf7+ Kh6 5. h5 a6 6. d4+ g5 7. hxg6#
  
  ```
  
  
  ---
  
  