Answers.Body: <pre><code>[Title &quot;&quot;]
  [Fen &quot;8/8/8/8/3K2N1/7R/4p1p1/4qkqR w - - 0 1&quot;]
  
  1. Ne3+ Kf2 2. Ng4+ Kf1+ 3. Ne3+ Kf2 4. Ng4+ Kf1+
  </code></pre>
  
Answers.ContentLicense: CC BY-SA 4.0
Answers.CreationDate: 2024-12-10T09:18:17.060Z
Answers.Text: That's great very satisfactory +1 thank you. I wonder now if it's possible to do it in a way that the Black check is forcing as well? Here wR1 pins bQ which stops it capturing, but White might play Rxg1 instead of Ne3
Answers.UserDisplayName: Laska
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Answers.CreationDate: 2024-12-10T09:25:32.990Z
Answers.Text: @Laska 1.Rxg1 Kxg1 would be losing for White, so while it's not the only legal move, taking the perpetual check is forced in order to save the game.
Answers.UserDisplayName: Evargalo
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Answers.CreationDate: 2024-12-10T09:29:26.787Z
Answers.Text: @evargalo Yes totally. However, I'm looking to get as close to a determinate loop as possible, i.e. 3/4 moves (or (n+1)/(2n)) entail a specific response
Answers.UserDisplayName: Laska
Answers.ContentLicense: CC BY-SA 4.0
Answers.CreationDate: 2024-12-10T09:57:11.557Z
Answers.Text: @Laska Interesting question! I can't see a way to adapt this construction, at least, to get more than half the moves forced. White's checking piece will always be able to move to the square vacated by the king (3. Nf2). And to prevent Black's checking piece from taking the white blocking piece, White needs another piece which will itself have a move (2. Rxg1+).
Answers.UserDisplayName: James Martin
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Answers.CreationDate: 2024-12-10T10:10:11.727Z
Answers.Text: Impossible for the same reason - no cyclic pin chains, i.e. one capture is always possible. But I think it is possible to have "more" forced moves. >50%? I will look into it immediately :-)
Answers.UserDisplayName: Hauke Reddmann
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Answers.CreationDate: 2024-12-10T21:33:38.950Z
Answers.Text: Best I could come up with: rB3KNq/4RBp1/3b2Pp/3P1kpP/b2p1r2/5P2/8/8 w - - 0 1 White has two alternatives (the wrong is a quick mate). The first one *might* be forced with a different battery, the second not (White can always move to the square the king left). 1.Be6+ (Be8??) Ke5 2.Bf7+ (Bf5??) Kf5 =
Answers.UserDisplayName: Hauke Reddmann
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Answers.CreationDate: 2024-12-10T21:45:14.983Z
Answers.Text: 8/3p4/rp1P4/N2qp3/KB1kr3/P2p4/2RP4/3b4  - different idea to force Black (one double check), same problem. I'll try on...
Answers.UserDisplayName: Hauke Reddmann
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Answers.CreationDate: 2024-12-10T08:44:07.540Z
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Answers.UserDisplayName: James Martin
Body: <p>I am looking for a sequence of White checks which forces a draw by perpetual check. And critically at least one (but not all) of the Black responses must also be a check.</p>
  <p>Ideally the Black check should force the White response. So out of e.g. 4 moves in a cycle, 3 are forcing checks. Or if the cycle is longer n+1 out of 2n moves are forcing checks.</p>
  <p>Does anyone know, or can construct such a pattern, please? Or prove that it's impossible?</p>
  <p>(Note: it is already known that there is no infinite chain of consecutive checks possible in orthodox chess. That's not the subject of this question - please don't pursue it here.)</p>
  
Tags: <draw><perpetual><construction-task>
Title: White perpetual check, where Black manages a check too?
ThreadText: # White perpetual check, where Black manages a check too?
  
  (Asked by: username_0 on 2024-12-10)
  
  I am looking for a sequence of White checks which forces a draw by perpetual check. And critically at least one (but not all) of the Black responses must also be a check.
  
  Ideally the Black check should force the White response. So out of e.g. 4 moves in a cycle, 3 are forcing checks. Or if the cycle is longer n+1 out of 2n moves are forcing checks.
  
  Does anyone know, or can construct such a pattern, please? Or prove that it's impossible?
  
  (Note: it is already known that there is no infinite chain of consecutive checks possible in orthodox chess. That's not the subject of this question - please don't pursue it here.)
  
  **Tags:** draw, perpetual, construction-task
  
  
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  ## 1 answers
  
  ### Answer by username_1 on 2024-12-10. Score: 24
  
  [Title ""]
  [Fen "8/8/8/8/3K2N1/7R/4p1p1/4qkqR w - - 0 1"]
  
  1. Ne3+ Kf2 2. Ng4+ Kf1+ 3. Ne3+ Kf2 4. Ng4+ Kf1+
  
  > **Comments:**
  > **username_0**: That's great very satisfactory +1 thank you. I wonder now if it's possible to do it in a way that the Black check is forcing as well? Here wR1 pins bQ which stops it capturing, but White might play Rxg1 instead of Ne3  
  > **username_2**: @username_0 1.Rxg1 Kxg1 would be losing for White, so while it's not the only legal move, taking the perpetual check is forced in order to save the game.  
  > **username_0**: @evargalo Yes totally. However, I'm looking to get as close to a determinate loop as possible, i.e. 3/4 moves (or (n+1)/(2n)) entail a specific response  
  > **username_1**: @username_0 Interesting question! I can't see a way to adapt this construction, at least, to get more than half the moves forced. White's checking piece will always be able to move to the square vacated by the king (3. Nf2). And to prevent Black's checking piece from taking the white blocking piece, White needs another piece which will itself have a move (2. Rxg1+).  
  > **username_3**: Impossible for the same reason - no cyclic pin chains, i.e. one capture is always possible. But I think it is possible to have "more" forced moves. >50%? I will look into it immediately :-)  
  > **username_3**: Best I could come up with: rB3KNq/4RBp1/3b2Pp/3P1kpP/b2p1r2/5P2/8/8 w - - 0 1 White has two alternatives (the wrong is a quick mate). The first one *might* be forced with a different battery, the second not (White can always move to the square the king left). 1.Be6+ (Be8??) Ke5 2.Bf7+ (Bf5??) Kf5 =  
  > **username_3**: 8/3p4/rp1P4/N2qp3/KB1kr3/P2p4/2RP4/3b4  - different idea to force Black (one double check), same problem. I'll try on...  
  
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