Answers.Body: <p>For a partial answer, here are a semi-unique sequence sin 11 moves. They are no doubt revealing of the true solution's strategy.</p>
  <pre><code>[FEN &quot;&quot;]
  
  1. e4 h5 2. Qxh5 Rxh5 3. g4 Re5 4. Bc4 Rxe4+ 5. Kf1 Re1+ 6. Kg2 Rxc1 7. g5 Re1 8. Be6 Rxe6 9. g6 Rxg6+ 10. Kf1 Rh6 11. Ke1 Rh8
  </code></pre>
  <p>Or this.</p>
  <pre><code>[FEN &quot;&quot;]
  
  1. e3 h5 2. Qxh5 Rxh5 3. g3 Rh3 4. Bd3 Rxg3 5. Kf1 Rxe3 6. Kg2 Re1 7. Bf5 Rxc1  8. Bg4 Re1 9. Bh3 Re3 10. Kf1 Rxh3 11. Ke1 Rh8
  </code></pre>
  <p>And this.</p>
  <pre><code>[FEN &quot;&quot;]
  
  1. e4 h5 2. Qxh5 Rxh5 3. g3 Re5 4. Bh3 Rxe4+ 5. Kf1 Re1+ 6. Kg2 Rxc1 7. Kf3 Re1  8. Kg2 Re3 9. Kf1 Rxg3 10. Ke2 Rxh3 11. Ke1 Rh8
  </code></pre>
  
Answers.ContentLicense: CC BY-SA 4.0
Answers.CreationDate: 2020-11-25T17:43:52.863Z
Answers.Text: Good experiments! But the actual solution is a lot shorter!
Answers.UserDisplayName: Laska
Answers.ContentLicense: CC BY-SA 4.0
Answers.CreationDate: 2020-11-25T17:31:07.313Z
Answers.LastActivityDate: 2020-11-25T18:37:24.533Z
Answers.LastEditDate: 2020-11-25T18:37:24.533Z
Answers.UserDisplayName: Rewan Demontay
Answers.Body: <p>I have no idea about this kind of problems, but my guess would be something like this.</p>
  <pre><code>[FEN &quot;&quot;]
  
  1. g4 h5 2. Bg2 hxg4 3. Bf3 gxf3 4. Kf1 fxe2+ 5. Kg2 exd1=R 6. Kf3 Rxc1 7. Ke2 Re1+ 8. Kxe1
  </code></pre>
  <p>Is that unique? I have no idea.</p>
  
Answers.ContentLicense: CC BY-SA 4.0
Answers.CreationDate: 2020-11-25T18:59:56.963Z
Answers.Text: @RewanDemontay thanks for the edit, how does that work? Simply adding [FEN ""] before the moves? And then presumably enter the position in the quotation marks if it's not the starting position.
Answers.UserDisplayName: koedem
Answers.ContentLicense: CC BY-SA 4.0
Answers.CreationDate: 2020-11-25T19:10:51.807Z
Answers.Text: Very nice - and yes it’s unique. Can you make sure this is concealed by spoiler protection, so others can have a go
Answers.UserDisplayName: Laska
Answers.ContentLicense: CC BY-SA 4.0
Answers.CreationDate: 2020-11-25T19:16:39.653Z
Answers.Text: @Laska do you happen to know if there is a way to hide a diagram? So apparently spoilers can be used through the usage of >! ? But then the diagram is gone again.
Answers.UserDisplayName: koedem
Answers.ContentLicense: CC BY-SA 4.0
Answers.CreationDate: 2020-11-26T08:54:04.190Z
Answers.Text: @koedem I don't know how to hide a diagram: maybe ask in meta
Answers.UserDisplayName: Laska
Answers.ContentLicense: CC BY-SA 4.0
Answers.CreationDate: 2020-11-26T09:29:50.210Z
Answers.Text: Spoilers are very limited in what formatting they support; the replayer won't work in them. I feel that people who visit the page *know* there must be solutions below, so a spoiler isn't really necessary.
Answers.UserDisplayName: Glorfindel
Answers.ContentLicense: CC BY-SA 4.0
Answers.CreationDate: 2020-11-25T18:23:09.963Z
Answers.LastActivityDate: 2020-11-25T19:14:31.880Z
Answers.LastEditDate: 2020-11-25T19:14:31.880Z
Answers.UserDisplayName: koedem
Body: <p>&quot;Homebase&quot; is where all the surviving pieces are apparently on their starting squares. Here is a very easy new example proof game: can you find the unique shortest game that leads to this position?</p>
  <pre><code>[Title &quot;A.Buchanan 26-11-2020 Facebook: shortest proof game?&quot;]
  [FEN &quot;rnbqkbnr/ppppppp1/8/8/8/8/PPPP1P1P/RN2K1NR w - - 0 1&quot;]
  </code></pre>
  <p>Yes c1 is empty!</p>
  
Tags: <problems><retrograde-analysis>
Title: How many moves needed to reach this position?
ThreadText: # How many moves needed to reach this position?
  
  (Asked by: username_0 on 2020-11-25)
  
  "Homebase" is where all the surviving pieces are apparently on their starting squares. Here is a very easy new example proof game: can you find the unique shortest game that leads to this position?
  [Title "A.Buchanan 26-11-2020 Facebook: shortest proof game?"]
  [FEN "rnbqkbnr/ppppppp1/8/8/8/8/PPPP1P1P/RN2K1NR w - - 0 1"]
  
  Yes c1 is empty!
  
  **Tags:** problems, retrograde-analysis
  
  
  ---
  
  ## 2 answers
  
  ### Answer by username_2 on 2020-11-25. Score: 4 | Accepted answer
  
  I have no idea about this kind of problems, but my guess would be something like this.
  [FEN ""]
  
  1. g4 h5 2. Bg2 hxg4 3. Bf3 gxf3 4. Kf1 fxe2+ 5. Kg2 exd1=R 6. Kf3 Rxc1 7. Ke2 Re1+ 8. Kxe1
  
  Is that unique? I have no idea.
  
  > **Comments:**
  > **username_2**: @RewanDemontay thanks for the edit, how does that work? Simply adding [FEN ""] before the moves? And then presumably enter the position in the quotation marks if it's not the starting position.  
  > **username_0**: Very nice - and yes it’s unique. Can you make sure this is concealed by spoiler protection, so others can have a go  
  > **username_2**: @username_0 do you happen to know if there is a way to hide a diagram? So apparently spoilers can be used through the usage of >! ? But then the diagram is gone again.  
  > **username_0**: @username_2 I don't know how to hide a diagram: maybe ask in meta  
  > **username_3**: Spoilers are very limited in what formatting they support; the replayer won't work in them. I feel that people who visit the page *know* there must be solutions below, so a spoiler isn't really necessary.  
  
  ---
  
  ### Answer by username_1 on 2020-11-25. Score: 2
  
  For a partial answer, here are a semi-unique sequence sin 11 moves. They are no doubt revealing of the true solution's strategy.
  [FEN ""]
  
  1. e4 h5 2. Qxh5 Rxh5 3. g4 Re5 4. Bc4 Rxe4+ 5. Kf1 Re1+ 6. Kg2 Rxc1 7. g5 Re1 8. Be6 Rxe6 9. g6 Rxg6+ 10. Kf1 Rh6 11. Ke1 Rh8
  
  Or this.
  [FEN ""]
  
  1. e3 h5 2. Qxh5 Rxh5 3. g3 Rh3 4. Bd3 Rxg3 5. Kf1 Rxe3 6. Kg2 Re1 7. Bf5 Rxc1  8. Bg4 Re1 9. Bh3 Re3 10. Kf1 Rxh3 11. Ke1 Rh8
  
  And this.
  [FEN ""]
  
  1. e4 h5 2. Qxh5 Rxh5 3. g3 Re5 4. Bh3 Rxe4+ 5. Kf1 Re1+ 6. Kg2 Rxc1 7. Kf3 Re1  8. Kg2 Re3 9. Kf1 Rxg3 10. Ke2 Rxh3 11. Ke1 Rh8
  
  > **Comments:**
  > **username_0**: Good experiments! But the actual solution is a lot shorter!  
  
  ---
  
  