Answers.Body: <p>Using a table base, this is easy to explain.</p>
  <p>In the first diagram it is lost in 3, 10 or 12 moves with optimal play because of the possibility of <code>Kf5</code>.
  All other white moves are drawn or lost.</p>
  <p><strong>Because white can cage the black K, it results in a win for white.</strong></p>
  <p><em>For simplicity I ignored alternate lines that where equally fast.</em></p>
  <pre><code>[Variant &quot;Antichess&quot;]
  [FEN &quot;5k2/8/8/8/6K1/8/8/3R4 w - - 0 1&quot;]
  
  1. Kf5 Kg7 {a R vs K end game is now certain} (1... Ke8 {loses faster} 2. Rd7 Kxd7 3. Ke6 Kxe6#) ( 1... Ke7 {loses faster} 2. Rd6 Kxd6 3. Ke5 Kxe5) (1... Kf7 {loses faster} 2. Ke6 Kxe6 3. Rd7 Kxd7#) (1... Kg8 {is the hardest try} 2. Re1 Kh7 3. Ke6 Kh6 4. Re4 Kh7 5. Re5 Kh8 6. Kf5 Kg8 7. Re6 Kh8 8. Rf6 Kg7 9. Rh6 Kxh6 10. Kg6 Kxg6#) 2. Kg6 Kxg6 {RvsK is lost for the K!} 3. Re1 Kg5 4. Re3 Kg6 5. Re4 Kg7 6. Re5 Kh8 7. Rf5 Kh7 8. Rf3 Kh6 9. Rf4 Kh7 10. Rf5 Kh8 11. Rf6 Kg7 12. Rf7 Kxf7#
  </code></pre>
  <p>The second diagram is drawn, because the black K can reach the e column which forces the white R from the d column. Because of this the K escapes from its cage and with optimal play it's a draw. According to the table base the possibilities seem endlessly, but they all draw.</p>
  <p>E.g. If we choose <code>Kf4</code> as the first move (for the parallelity with the first diagram), we can see that the e column must be abandoned within 3 moves to prevent a loss. Since black can't permanently shrink the cage on the K, there is no way to make progress.
  However, Black must constantly play accurate to keep the draw (e.g. only <code>1.Kf7</code> and <code>1.Ke8</code> are drawing), but with optimal play it is possible and eventually repetition or the 50 move rule will end the game in a draw.</p>
  <p><em>Other moves than <code>Kf4</code> are also drawn, just as it was in the first diagram.</em></p>
  <p><strong>Because white can't make progress to cage the black K, it is a draw.</strong></p>
  <pre><code>[Variant &quot;Antichess&quot;]
  [FEN &quot;5k2/8/8/8/8/6K1/8/3R4 w - - 0 1&quot;]
  
  1. Kf4 Kf7 (1... Ke8 2. Rd7 (2. Ra1 {forfeits the control of the e column.}) 2... Kxd7 {Is a well known draw}) 2. Ra1 {forfeits the control of the e column.} (2. Rd2 Ke8 3. Rd7 (3. Ra2 {forfeits the control of the e column.}) 3... Kxd7 {Is a well known draw})
  </code></pre>
  <p>Note that it will take a very strong Antichess player to not lose this as black.</p>
  
Answers.ContentLicense: CC BY-SA 4.0
Answers.CreationDate: 2023-07-19T09:12:49.033Z
Answers.LastActivityDate: 2023-07-19T09:12:49.033Z
Answers.UserDisplayName: IT M
Answers.Body: <p>in the upper position there is Kf5 Kg8 Re8 Kh8 Kg5 and the pattern continues</p>
  <p>the strategy is very simple:
  if KR loses king then it is a win
  if KR loses R and there is no immediate sacrifice of the king, it is a draw
  from that follows, KR can only win if he can force the king onto a square where he can follow with a king sacrifice - how is that possible?
  WK is on the 8th rank
  BK is on the 5th rank
  the WK needs to come to the 7th rank, ROOK sacrifice! then BK comes to the 6th rank, KING sacrifice
  there is no possibility to force the WK from the 7th to the 8th rank so if the king escapes the edge, under typical circumstances, it is a draw</p>
  
Answers.ContentLicense: CC BY-SA 4.0
Answers.CreationDate: 2023-06-18T08:15:12.933Z
Answers.Text: Can you include chessboards into your answer like I have in the question to make your answer more clear? At the moment, I have a hard time understanding what you are talking about.
Answers.UserDisplayName: Aiden Chow
Answers.ContentLicense: CC BY-SA 4.0
Answers.CreationDate: 2023-06-17T20:22:41.613Z
Answers.LastActivityDate: 2023-06-17T20:22:41.613Z
Answers.UserDisplayName: hello play chess
Body: <p><em>Note: This is not a question on standard chess, where obviously K+R vs K is a win for K+R.</em></p>
  <p>Here are two example K+R vs K positions in <strong>antichess</strong>, both having white to play and white having K+R.</p>
  <p>Position #1 (This is a winning position after Kf5 according to lichess's antichess engine):</p>
  <pre><code>[Title &quot;White to play and win - anti-chess&quot;]
  [FEN &quot;5k2/8/8/8/6K1/8/8/3R4 w - - 0 1&quot;]
  </code></pre>
  <p><a href="https://lichess.org/analysis/antichess/5k2/8/8/8/6K1/8/8/3R4_w_-_-_0_1?color=white" rel="nofollow noreferrer">Lichess analysis board</a></p>
  <p>Position #2 (This is a drawn position according to the same engine):</p>
  <pre><code>[Title &quot;White to play and draw - anti-chess&quot;]
  [FEN &quot;5k2/8/8/8/8/6K1/8/3R4 w - - 0 1&quot;]
  </code></pre>
  <p><a href="https://lichess.org/analysis/antichess/5k2/8/8/8/8/6K1/8/3R4_w_-_-_0_1?color=white" rel="nofollow noreferrer">Lichess analysis board</a></p>
  <hr />
  <p>In antichess, what are the principles / guidelines for determining whether or not a K+R vs K endgame is winning or a draw for the side with K+R?</p>
  
Comments.ContentLicense: CC BY-SA 4.0
Comments.CreationDate: 2023-06-12T07:09:59.427Z
Comments.Text: First of all, R vs K is won for R. This directly suggests that White should try to sacrifice the K. Black should threaten to throw the king to the rook. But that's one what my intuition says.
Comments.UserDisplayName: Hauke Reddmann
Comments.ContentLicense: CC BY-SA 4.0
Comments.CreationDate: 2023-06-12T19:54:26.437Z
Comments.Text: @HaukeReddmann Yes that seems to be a viable strategy for both players, but I think black has to be careful about throwing their K against white's R if white's K is nearby. There seems to be cases where white's K and R can collaborate in such a way to force black's K to the corner and put black in zugzwang, yet there are other cases where black's K seems to be able to escape and secure a draw. I would like a more detailed analysis on these cases.
Comments.UserDisplayName: Aiden Chow
Tags: <chess-variants><losing-chess>
Title: When is K vs K+R in antichess winning? How to win these endgames?
ThreadText: # When is K vs K+R in antichess winning? How to win these endgames?
  
  (Asked by: username_0 on 2023-06-10)
  
  *Note: This is not a question on standard username_3, where obviously K+R vs K is a win for K+R.*
  
  Here are two example K+R vs K positions in **antichess**, both having white to play and white having K+R.
  
  Position #1 (This is a winning position after Kf5 according to lichess's antichess engine):
  
  ```
  [Title "White to play and win - anti-username_3"]
  [FEN "5k2/8/8/8/6K1/8/8/3R4 w - - 0 1"]
  
  ```
  
  [Lichess analysis board](https://lichess.org/analysis/antichess/5k2/8/8/8/6K1/8/8/3R4_w_-_-_0_1?color=white)
  
  Position #2 (This is a drawn position according to the same engine):
  
  ```
  [Title "White to play and draw - anti-username_3"]
  [FEN "5k2/8/8/8/8/6K1/8/3R4 w - - 0 1"]
  
  ```
  
  [Lichess analysis board](https://lichess.org/analysis/antichess/5k2/8/8/8/8/6K1/8/3R4_w_-_-_0_1?color=white)
  
  ---
  
  In antichess, what are the principles / guidelines for determining whether or not a K+R vs K endgame is winning or a draw for the side with K+R?
  
  **Tags:** chess-variants, losing-chess
  
  > **Comments:**
  > **username_1**: First of all, R vs K is won for R. This directly suggests that White should try to sacrifice the K. Black should threaten to throw the king to the rook. But that's one what my intuition says.  
  > **username_0**: @username_1 Yes that seems to be a viable strategy for both players, but I think black has to be careful about throwing their K against white's R if white's K is nearby. There seems to be cases where white's K and R can collaborate in such a way to force black's K to the corner and put black in zugzwang, yet there are other cases where black's K seems to be able to escape and secure a draw. I would like a more detailed analysis on these cases.  
  
  ---
  
  ## 2 answers
  
  ### Answer by username_2 on 2023-07-19. Score: 1
  
  Using a table base, this is easy to explain.
  
  In the first diagram it is lost in 3, 10 or 12 moves with optimal play because of the possibility of `Kf5`.
  All other white moves are drawn or lost.
  
  **Because white can cage the black K, it results in a win for white.**
  
  *For simplicity I ignored alternate lines that where equally fast.*
  
  ```
  [Variant "Antichess"]
  [FEN "5k2/8/8/8/6K1/8/8/3R4 w - - 0 1"]
  
  1. Kf5 Kg7 {a R vs K end game is now certain} (1... Ke8 {loses faster} 2. Rd7 Kxd7 3. Ke6 Kxe6#) ( 1... Ke7 {loses faster} 2. Rd6 Kxd6 3. Ke5 Kxe5) (1... Kf7 {loses faster} 2. Ke6 Kxe6 3. Rd7 Kxd7#) (1... Kg8 {is the hardest try} 2. Re1 Kh7 3. Ke6 Kh6 4. Re4 Kh7 5. Re5 Kh8 6. Kf5 Kg8 7. Re6 Kh8 8. Rf6 Kg7 9. Rh6 Kxh6 10. Kg6 Kxg6#) 2. Kg6 Kxg6 {RvsK is lost for the K!} 3. Re1 Kg5 4. Re3 Kg6 5. Re4 Kg7 6. Re5 Kh8 7. Rf5 Kh7 8. Rf3 Kh6 9. Rf4 Kh7 10. Rf5 Kh8 11. Rf6 Kg7 12. Rf7 Kxf7#
  
  ```
  
  The second diagram is drawn, because the black K can reach the e column which forces the white R from the d column. Because of this the K escapes from its cage and with optimal play it's a draw. According to the table base the possibilities seem endlessly, but they all draw.
  
  E.g. If we choose `Kf4` as the first move (for the parallelity with the first diagram), we can see that the e column must be abandoned within 3 moves to prevent a loss. Since black can't permanently shrink the cage on the K, there is no way to make progress.
  However, Black must constantly play accurate to keep the draw (e.g. only `1.Kf7` and `1.Ke8` are drawing), but with optimal play it is possible and eventually repetition or the 50 move rule will end the game in a draw.
  
  *Other moves than `Kf4` are also drawn, just as it was in the first diagram.*
  
  **Because white can't make progress to cage the black K, it is a draw.**
  
  ```
  [Variant "Antichess"]
  [FEN "5k2/8/8/8/8/6K1/8/3R4 w - - 0 1"]
  
  1. Kf4 Kf7 (1... Ke8 2. Rd7 (2. Ra1 {forfeits the control of the e column.}) 2... Kxd7 {Is a well known draw}) 2. Ra1 {forfeits the control of the e column.} (2. Rd2 Ke8 3. Rd7 (3. Ra2 {forfeits the control of the e column.}) 3... Kxd7 {Is a well known draw})
  
  ```
  
  Note that it will take a very strong Antichess player to not lose this as black.
  
  
  ---
  
  ### Answer by username_3 on 2023-06-17. Score: 1
  
  in the upper position there is Kf5 Kg8 Re8 Kh8 Kg5 and the pattern continues
  
  the strategy is very simple:
  if KR loses king then it is a win
  if KR loses R and there is no immediate sacrifice of the king, it is a draw
  from that follows, KR can only win if he can force the king onto a square where he can follow with a king sacrifice - how is that possible?
  WK is on the 8th rank
  BK is on the 5th rank
  the WK needs to come to the 7th rank, ROOK sacrifice! then BK comes to the 6th rank, KING sacrifice
  there is no possibility to force the WK from the 7th to the 8th rank so if the king escapes the edge, under typical circumstances, it is a draw
  
  > **Comments:**
  > **username_0**: Can you include chessboards into your answer like I have in the question to make your answer more clear? At the moment, I have a hard time understanding what you are talking about.  
  
  ---
  
  