Answers.Body: <p>It's hard to provide full analysis, but I'd say yes with almost all certainty. One of the main difficulties the stronger side encounters on this endgame is getting to use the bishops to block checks on the right squares. This leveled-up bishop can block checks on any square while the king and rook corner the enemy king</p>
  
Answers.ContentLicense: CC BY-SA 4.0
Answers.CreationDate: 2023-01-21T01:17:16.350Z
Answers.Text: Also K+B/K is a draw but K+B*/K is a win so the stronger side can block checks with the Rook, and more generally offer or threaten Rook trades, so the defended loses an important tactical resource.
Answers.UserDisplayName: Noam D. Elkies
Answers.ContentLicense: CC BY-SA 4.0
Answers.CreationDate: 2023-01-20T18:47:07.383Z
Answers.LastActivityDate: 2023-01-20T18:47:07.383Z
Answers.UserDisplayName: David
Body: <p>I've recently been trying to learn the queen vs rook and rook and bishop vs rook endgames, and I've found it interesting how close the margin of victory vs draw is. I was thinking about whether the bishop's color lock is the reason it can't win. So what if we gave the bishop its shogi promotion that allows it to additionally move like a king? Does this promoted bishop give its rook the support it needs to overcome the enemy rook?</p>
  <p>Also, as a related question, is there a more general resource for analyzing endgames with nonstandard pieces?</p>
  
Comments.ContentLicense: CC BY-SA 4.0
Comments.CreationDate: 2023-01-20T17:35:08.113Z
Comments.Text: Probably yes, and it should be possible to answer this by generating the same kind of "tablebase" that solved all positions with at most 5 (and now 6, 7, and even 8 !) men on the board.  I wouldn't be too surprised if replacing the Bishop by a platinum general -- or whatever you call a non-royal piece moves like a King -- is already enough to give a win.  [Wikipedia <https://en.wikipedia.org/wiki/Fairy_chess_piece> lists several names for that piece, including Sage, Fool, Man(n), and Erlking; I suggested "platinum general" because of your Shogi reference.]
Comments.UserDisplayName: Noam D. Elkies
Tags: <endgame><checkmate><unorthodox-pieces>
Title: Rook and promoted Bishop vs Rook endgame--forced win or draw?
ThreadText: # Rook and promoted Bishop vs Rook endgame--forced win or draw?
  
  (Asked by: username_0 on 2023-01-20)
  
  I've recently been trying to learn the queen vs rook and rook and bishop vs rook endgames, and I've found it interesting how close the margin of victory vs draw is. I was thinking about whether the bishop's color lock is the reason it can't win. So what if we gave the bishop its shogi promotion that allows it to additionally move like a king? Does this promoted bishop give its rook the support it needs to overcome the enemy rook?
  
  Also, as a related question, is there a more general resource for analyzing endgames with nonstandard pieces?
  
  **Tags:** endgame, checkmate, unorthodox-pieces
  
  > **Comments:**
  > **username_1**: Probably yes, and it should be possible to answer this by generating the same kind of "tablebase" that solved all positions with at most 5 (and now 6, 7, and even 8 !) men on the board.  I wouldn't be too surprised if replacing the Bishop by a platinum general -- or whatever you call a non-royal piece moves like a King -- is already enough to give a win.  [Wikipedia <https://en.wikipedia.org/wiki/Fairy_chess_piece> lists several names for that piece, including Sage, Fool, Man(n), and Erlking; I suggested "platinum general" because of your Shogi reference.]  
  
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  ## 1 answers
  
  ### Answer by username_2 on 2023-01-20. Score: 1
  
  It's hard to provide full analysis, but I'd say yes with almost all certainty. One of the main difficulties the stronger side encounters on this endgame is getting to use the bishops to block checks on the right squares. This leveled-up bishop can block checks on any square while the king and rook corner the enemy king
  
  > **Comments:**
  > **username_1**: Also K+B/K is a draw but K+B*/K is a win so the stronger side can block checks with the Rook, and more generally offer or threaten Rook trades, so the defended loses an important tactical resource.  
  
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