Answers.Body: <p>It can be proven that <strong>10 moves, or 20 plies,</strong> is the least possible.</p>
  <pre><code>[Title &quot;&quot;]
  [FEN &quot;&quot;]
  
  1. f3 f6 2. Kf2 Kf7 3. Kg3 Ke6 4. h3 h6 5. Kh4 Kf5 6. Kh5 Kf4 7. Kg6 Kg3 8. Rh2  Rh7 9. Kxh7 Kxh2 10. Kh8 Kh1
  </code></pre>
  <p>Here is the proof, listed in a logical order.</p>
  <p><strong>Observations Of Proof</strong></p>
  <ol>
  <li>Both kings must make at least seven moves to get to the other rank, so that's 14 plies off the bat.</li>
  <li>Each side must move a pawn move to release a king, which costs 2 plies in further total.</li>
  <li>Each side must move a piece to unguard a square for the other king, also costing 2 plies.</li>
  <li>Finally, at least one more pawn move by both sides is required in order to let each king bypass the pawn structure, and that amounts to 2 plies.</li>
  </ol>
  <p>In conclusion, 14+2+2+2=20 plies, so it is indeed the minimum possible.</p>
  
Answers.ContentLicense: CC BY-SA 4.0
Answers.CreationDate: 2020-11-21T04:43:41.440Z
Answers.LastActivityDate: 2021-01-26T17:15:07.863Z
Answers.LastEditDate: 2021-01-26T17:15:07.863Z
Answers.UserDisplayName: Rewan Demontay
Body: <p>Say that both players collaborate to get White's king to the eighth rank and Black's king to the first. What's the shortest sequence of moves that achieves this?</p>
  
Tags: <problems><records>
Title: Fastest way to get both kings to the other side of the board?
ThreadText: # Fastest way to get both kings to the other side of the board?
  
  (Asked by: username_0 on 2020-11-21)
  
  Say that both players collaborate to get White's king to the eighth rank and Black's king to the first. What's the shortest sequence of moves that achieves this?
  
  **Tags:** problems, records
  
  
  ---
  
  ## 1 answers
  
  ### Answer by username_1 on 2020-11-21. Score: 4 | Accepted answer
  
  It can be proven that **10 moves, or 20 plies,** is the least possible.
  
  ```
  [Title ""]
  [FEN ""]
  
  1. f3 f6 2. Kf2 Kf7 3. Kg3 Ke6 4. h3 h6 5. Kh4 Kf5 6. Kh5 Kf4 7. Kg6 Kg3 8. Rh2  Rh7 9. Kxh7 Kxh2 10. Kh8 Kh1
  
  ```
  
  Here is the proof, listed in a logical order.
  
  **Observations Of Proof**
  
  1. Both kings must make at least seven moves to get to the other rank, so that's 14 plies off the bat.
  2. Each side must move a pawn move to release a king, which costs 2 plies in further total.
  3. Each side must move a piece to unguard a square for the other king, also costing 2 plies.
  4. Finally, at least one more pawn move by both sides is required in order to let each king bypass the pawn structure, and that amounts to 2 plies.
  
  In conclusion, 14+2+2+2=20 plies, so it is indeed the minimum possible.
  
  
  ---
  
  