Answers.Body: <p>Kingside castling, 8.5 moves (fastest; no way for a king to reach the last rank any faster than this.)</p>
  
  <pre><code>[FEN ""]
  1. e4 d6 2. b4 Kd7 3. Nh3 Kc6 4. Bb5+ Kxb5 5. Nc3+ Kxb4 6. Ba3+ Kxa3 7. Qh5 Kb2 8. Qb5+ Kxa1 9. O-O#
  </code></pre>
  
  <p>Queenside castling: 8.5 moves (again, fastest.)</p>
  
  <pre><code>[FEN ""]
  1. d4 e6 2. g4 Ke7 3. Na3 Kf6 4. Bg5+ Kxg5 5. Nf3+ Kxg4 6. Bh3+ Kxh3 7. Qd3 Kg2 8. Qg6+ Kxh1 9. O-O-O#
  </code></pre>
  
  <p>There you have it. The theoretical fastest is 8.0 moves if you try to let black deliver mate instead of white, but I couldn't find a way to set up the mating net or to avoid locking the king out. Feel free to try.</p>
  
Answers.ContentLicense: CC BY-SA 4.0
Answers.CreationDate: 2019-02-28T17:58:56.583Z
Answers.Text: @Ywapom: The enemy king needs 8 moves to reach the other side of the board (7 king moves and one pawn move to make space).
Answers.UserDisplayName: user1583209
Answers.ContentLicense: CC BY-SA 4.0
Answers.CreationDate: 2019-02-28T18:17:17.697Z
Answers.Text: ah, so is this the fastest vertical mate?
Answers.UserDisplayName: Ywapom
Answers.ContentLicense: CC BY-SA 4.0
Answers.CreationDate: 2019-02-28T03:27:20.083Z
Answers.LastActivityDate: 2019-02-28T10:15:12.117Z
Answers.LastEditDate: 2019-02-28T10:15:12.117Z
Answers.UserDisplayName: Remellion
Answers.Body: <p>I know this thread is old, but here is my improvement to kingside castling-8.0 moves. Black even has to do one useless waiting move (Ng4).</p>
  <pre><code>[FEN &quot;&quot;]
  1. e3 e5 2. Ke2 c5 3. Kd3 Bd6 4. Ke4 Nh6 5. Kd5 Ng4 6. Kxd6 Qf6+ 7. Kc7 Qb6+ 8. Kxc8 O-O#
  </code></pre>
  <p>Queenside castling can be proven to be impossible in 8.0.</p>
  
Answers.ContentLicense: CC BY-SA 4.0
Answers.CreationDate: 2020-04-23T07:14:20.937Z
Answers.LastActivityDate: 2020-08-17T02:42:57.723Z
Answers.LastEditDate: 2020-08-17T02:42:57.723Z
Answers.UserDisplayName: Roger Johnsson
Body: <p>I wish to know the fastest possible castling checkmate, both queenside and kingside, that is horizontal.</p>
  <p>See my question about <a href="http://chess.stackexchange.com/q/23843">vertical checkmates.</a>.</p>
  
Tags: <checkmate><problems><castling><records>
Title: What is the fastest horizontal checkmate for both castlings?
ThreadText: # What is the fastest horizontal checkmate for both castlings?
  
  (Asked by: username_0 on 2019-02-27)
  
  I wish to know the fastest possible castling checkmate, both queenside and kingside, that is horizontal.
  
  See my question about [vertical checkmates.](http://chess.stackexchange.com/q/23843).
  
  **Tags:** checkmate, problems, castling, records
  
  
  ---
  
  ## 2 answers
  
  ### Answer by username_4 on 2020-04-23. Score: 6 | Accepted answer
  
  I know this thread is old, but here is my improvement to kingside castling-8.0 moves. Black even has to do one useless waiting move (Ng4).
  [FEN ""]
  1. e3 e5 2. Ke2 c5 3. Kd3 Bd6 4. Ke4 Nh6 5. Kd5 Ng4 6. Kxd6 Qf6+ 7. Kc7 Qb6+ 8. Kxc8 O-O#
  
  Queenside castling can be proven to be impossible in 8.0.
  
  
  ---
  
  ### Answer by username_1 on 2019-02-28. Score: 4
  
  Kingside castling, 8.5 moves (fastest; no way for a king to reach the last rank any faster than this.)
  [FEN ""]
  1. e4 d6 2. b4 Kd7 3. Nh3 Kc6 4. Bb5+ Kxb5 5. Nc3+ Kxb4 6. Ba3+ Kxa3 7. Qh5 Kb2 8. Qb5+ Kxa1 9. O-O#
  
  Queenside castling: 8.5 moves (again, fastest.)
  [FEN ""]
  1. d4 e6 2. g4 Ke7 3. Na3 Kf6 4. Bg5+ Kxg5 5. Nf3+ Kxg4 6. Bh3+ Kxh3 7. Qd3 Kg2 8. Qg6+ Kxh1 9. O-O-O#
  
  There you have it. The theoretical fastest is 8.0 moves if you try to let black deliver mate instead of white, but I couldn't find a way to set up the mating net or to avoid locking the king out. Feel free to try.
  
  > **Comments:**
  > **username_2**: @username_3: The enemy king needs 8 moves to reach the other side of the board (7 king moves and one pawn move to make space).  
  > **username_3**: ah, so is this the fastest vertical mate?  
  
  ---
  
  