Answers.Body: <p><strong>The key word in the rule is "securely".</strong> </p>
  
  <p>Meaning, that there is nothing the opponent can do to lift the blockade. </p>
  
  <p>In the posted position, white has to play 1. Ng6  - otherwise black will play 1. .. g5 and be beyond the Troitzky line - achieving draw immediately.</p>
  
  <p>Subsequently, the black king will march toward the pawn, starting with 1. .. Kc5 and force the g6 knight away, as white is not in time to defend it, neither with the king nor the other knight. Then, g5 will and draw will follow.</p>
  
  <p>Thus, the position appears to be covered by the rule in its current wording, as the pawn is <strong>not securely blockaded</strong>.</p>
  
  <p><strong>EDIT - answering to the comment.</strong></p>
  
  <pre><code>4N3/6p1/8/8/1k5N/8/8/7K w - - 0 1
  
  1. Ng6 Kc5 2. Kg2 (2. Nc7 Kd6 3. Nb5+ (3. Ne8+ {pointless}) Ke6 {white is one move short of getting the other knight to e5} 4. Nd4+ Kf6 {white must move the knight away and g5 follows}) Kd5 Kg3 Ke6 4. Kg4 (4. Nf4+ Ke7 {white has to move the knight away and g5 follows}) (4. Nc7+ Kf7 {white is not in time to defend the knight, g5 will inevitably follow after a couple checks}) Kf7 {white cannot defend both knights}
  </code></pre>
  
  <p><strong>EDIT 2</strong></p>
  
  <p>As for the later added positions, I believe they are all covered by ETD's answer.</p>
  
Answers.ContentLicense: CC BY-SA 3.0
Answers.CreationDate: 2015-06-22T18:06:05.573Z
Answers.Text: Well actually the king is in time to defend if the knight attacks. The knight needs 4 moves to attack and in the same 4 moves the king can move unhindered up th h file to protect.
Answers.UserDisplayName: Martin Rattigan
Answers.ContentLicense: CC BY-SA 3.0
Answers.CreationDate: 2015-06-22T18:09:20.787Z
Answers.Text: @MartinRattigan I'll add diagram & moves in a moment to demonstrate what I mean.
Answers.UserDisplayName: GloriaVictis
Answers.ContentLicense: CC BY-SA 3.0
Answers.CreationDate: 2015-06-22T18:12:01.127Z
Answers.Text: @MartinRattigan, I'm not sure what line you have in mind exactly, but if you're saying the white king has time to head up and defend the g6 knight to maintain the blockade, that isn't so, e.g. `1.Ng6 Kc5 2.Kh2 Kd5 3.Kh3 Ke6 4.Kh4 Kf7` and one of the knights will be lost.
Answers.UserDisplayName: ETD
Answers.ContentLicense: CC BY-SA 3.0
Answers.CreationDate: 2015-06-22T18:15:47.503Z
Answers.Text: For "knight needs 4 moves" in the above read "black king needs 4 moves". (Sorry, senility I think.)
Answers.UserDisplayName: Martin Rattigan
Answers.ContentLicense: CC BY-SA 3.0
Answers.CreationDate: 2015-06-22T18:23:35.110Z
Answers.Text: I agree that one of the knights will be lost in the process. So you have a valid point. This is the first vote of confidence so far. Thank you. I will add some extra positions.
Answers.UserDisplayName: Martin Rattigan
Answers.ContentLicense: CC BY-SA 3.0
Answers.CreationDate: 2015-06-22T18:39:01.817Z
Answers.Text: Sorry I seem to have lost the boards. Where is the documentation for producing these?
Answers.UserDisplayName: Martin Rattigan
Answers.ContentLicense: CC BY-SA 3.0
Answers.CreationDate: 2015-06-22T18:50:45.123Z
Answers.Text: By the way since this is a _poll_ rather than a question I won't actually accept any of the answers, but that is not to say that I find them unsatisfactory.
Answers.UserDisplayName: Martin Rattigan
Answers.ContentLicense: CC BY-SA 3.0
Answers.CreationDate: 2015-06-22T22:20:44.920Z
Answers.Text: Would you then say that the h4 pawn is not securely blockaded in this position? Black can force white to lift the blockade (and lose a knight).                                                                                   8/8/8/8/7p/1K5N/5N2/1k6 w - - 0 1
Answers.UserDisplayName: Martin Rattigan
Answers.ContentLicense: CC BY-SA 3.0
Answers.CreationDate: 2015-06-22T23:06:49.157Z
Answers.Text: Here is a diagram for the above comment.       [fen "8/8/8/8/7p/1K5N/5N2/1k6 w - - 0 1"]
      [White "White"]
      [Black "to Move and win"]
Answers.UserDisplayName: Martin Rattigan
Answers.ContentLicense: CC BY-SA 3.0
Answers.CreationDate: 2015-06-22T23:20:37.807Z
Answers.Text: Giving the diagram up for the time being
Answers.UserDisplayName: Martin Rattigan
Answers.ContentLicense: CC BY-SA 3.0
Answers.CreationDate: 2015-06-23T23:36:02.433Z
Answers.Text: I agree that the first position would never be regarded as an exception. to the wording. This position was a brain malfunction on my part. I had analysed a related position shortly before in which Kd5 was losing for black and somehow  assumed it still was. I looked no further than Kc5-c6.
Answers.UserDisplayName: Martin Rattigan
Answers.ContentLicense: CC BY-SA 3.0
Answers.CreationDate: 2015-06-22T17:52:21.110Z
Answers.LastActivityDate: 2015-06-22T19:28:32.537Z
Answers.LastEditDate: 2015-06-22T19:28:32.537Z
Answers.UserDisplayName: GloriaVictis
Answers.Body: <p>I believe that GloriaVictis' answer addresses your first position very well, in that the pawn is not actually <em>securely</em> blockaded in that case; Black can force the further advance of the pawn.</p>
  
  <p>Your other positions are also susceptible to an insecure blockade, or are special in that, say, one of the knights is doomed to be lost, or else cannot participate in the play without capturing the pawn, yielding a draw in either case. For instance, position (4):</p>
  
  <pre><code>[fen "7N/2p5/2N5/3K2k1/8/8/8/8 b - - 0 1"]
  
  1...Kf6 {The knight cannot be saved except by allowing the pawn to advance.} 2.Ne5 (2.Ke4 Kg7) c5 3.Nhf7
  </code></pre>
  
  <p>So, one could insist that the wording cited in your question be strengthened to say something like, "the pawn is securely blockaded <em>and neither of the knights faces imminent capture, or is forced to capture the pawn in order to participate, etc.</em>." Ultimately, that is perhaps a matter of taste; I think most would instead say that these are clearly recognizable as special cases which the wording you cite need not attempt to address. </p>
  
Answers.ContentLicense: CC BY-SA 3.0
Answers.CreationDate: 2015-06-22T19:06:49.703Z
Answers.Text: Yes, except that the white king can prevent an attack on either knight in position 2. and black cannot force white to take the pawn.
Answers.UserDisplayName: Martin Rattigan
Answers.ContentLicense: CC BY-SA 3.0
Answers.CreationDate: 2015-06-22T19:10:08.057Z
Answers.Text: But again, thank you for your response. Another vote of confidence in the wording.
Answers.UserDisplayName: Martin Rattigan
Answers.ContentLicense: CC BY-SA 3.0
Answers.CreationDate: 2015-06-22T19:10:18.703Z
Answers.Text: Position 2 is what I had in mind when I wrote, "or is forced to capture the pawn in order to participate." For that position, Black doesn't need to do anything at all, and certainly doesn't need to bother attacking a knight. The white knight on a8 is trapped forever, unless White captures the pawn (draw), or the knight goes to b6 and is captured. Black can literally just move the king around willy-nilly and have a draw in that position.
Answers.UserDisplayName: ETD
Answers.ContentLicense: CC BY-SA 3.0
Answers.CreationDate: 2015-06-22T19:30:23.237Z
Answers.Text: As white I wouldn't take the pawn unless I were playing against an EGTB. If white can immobilize the king on h1 or h8 then the pawn is forced forward and black loses.
Answers.UserDisplayName: Martin Rattigan
Answers.ContentLicense: CC BY-SA 3.0
Answers.CreationDate: 2015-06-22T19:40:48.907Z
Answers.Text: @MartinRattigan, I'm not sure how you're concluding Black loses even in that case. Say Black's king gets immobilized on h8 (by a white knight on f6 and king on f7), and so has to play `1...c5` freeing the a8 knight. Fine, but the pawn will also be able to advance to c4 in that scenario, and Black should be able to draw. But in any case, we're veering off the topic of your question.
Answers.UserDisplayName: ETD
Answers.ContentLicense: CC BY-SA 3.0
Answers.CreationDate: 2015-06-22T20:17:56.540Z
Answers.Text: The second knight can deliver mate before the pawn queens if the king is immobilised before the pawn moves.
Answers.UserDisplayName: Martin Rattigan
Answers.ContentLicense: CC BY-SA 3.0
Answers.CreationDate: 2015-06-22T20:22:05.280Z
Answers.Text: But to stick to the topic, I don't think what we did discuss is adequately covered just by the phrase "securely blockaded".
Answers.UserDisplayName: Martin Rattigan
Answers.ContentLicense: CC BY-SA 3.0
Answers.CreationDate: 2015-06-22T20:31:11.690Z
Answers.Text: And actually my whole point is that this position _is_ a draw when the rule appears to say it should be a win for White.
Answers.UserDisplayName: Martin Rattigan
Answers.ContentLicense: CC BY-SA 3.0
Answers.CreationDate: 2015-06-22T22:19:56.077Z
Answers.Text: @MartinRattigan, I concur re: the immobilized king in Position 2 (though it's indeed moot since the stalemate in the corner can't be forced with only one knight participating beforehand). And I know your point is that the position is a draw; I'm less inclined to say that the rule says it should be a win for white. The way I think of that position is that, in essence, White only has one knight since the other is mechanically trapped out of play. ... (cont'd)
Answers.UserDisplayName: ETD
Answers.ContentLicense: CC BY-SA 3.0
Answers.CreationDate: 2015-06-22T22:21:48.863Z
Answers.Text: (cont'd) ... At the end of the day, there is of course no cut-and-dried answer, since we're talking about textual interpretation. What I think mine and GloriaVictis' answers attempt to show is how the wording as given makes perfect sense when considered against the backdrop of an appropriate ambient chess-playing view of the scenarios. (E.g. I don't see position 2 as something that needs to be worried about for the reason I state above, that White really doesn't have two healthy knights to begin with in that position. All this is of course a matter of perspective.)
Answers.UserDisplayName: ETD
Answers.ContentLicense: CC BY-SA 3.0
Answers.CreationDate: 2015-06-22T22:45:35.713Z
Answers.Text: The stalemate in the corner can't be forced from this position (it's drawn), but after 1.Ne5 it's conceivable that black could wander (willy-nilly) into a cornerable position (after all Karpov did exactly that against Topalov in 2001).
Answers.UserDisplayName: Martin Rattigan
Answers.ContentLicense: CC BY-SA 3.0
Answers.CreationDate: 2015-06-24T09:15:12.427Z
Answers.Text: ETD, you said "though it's indeed moot since the stalemate in the corner can't be forced with only one knight participating beforehand. I tried position 2. against Rybka and it blew it at the first attempt on move 2 (though not in the way I suggested). Game went 1. Ne5 Kg8 2. Ke6 c5 3. Nc4 Kg7.
Answers.UserDisplayName: Martin Rattigan
Answers.ContentLicense: CC BY-SA 3.0
Answers.CreationDate: 2015-06-24T11:01:22.007Z
Answers.Text: @EDT - Thought you might be interested in the last comment. (I just found out what the "@" symbol does.)
Answers.UserDisplayName: Martin Rattigan
Answers.ContentLicense: CC BY-SA 3.0
Answers.CreationDate: 2015-06-24T11:24:11.070Z
Answers.Text: @EDT. It lasted a bit longer on its second go, but it could take some time to get an example where it consistently uses your suggested defence. I don't believe the pawn was forced forward here either. 1. Ne5 Kg8 2. Nc4 Kh7 3. Ne3 Kh6 4.
  Ng4+ Kh5 5. Kf5 Kh4 6. Nf6 Kg3 7. Ke4 Kf2 8. Kd4 Kf3 9. Nd5 c5+ 10. Kc4 Kg4 11.
  Nc3 Kh4 12. Nb6 Kg4 13. Kd5 c4
Answers.UserDisplayName: Martin Rattigan
Answers.ContentLicense: CC BY-SA 3.0
Answers.CreationDate: 2015-06-24T11:27:23.717Z
Answers.Text: @EDT. By the way, the pawn past the Troitsky line where I stopped, but its OK with the black king  out of the a1 coirner.
Answers.UserDisplayName: Martin Rattigan
Answers.ContentLicense: CC BY-SA 3.0
Answers.CreationDate: 2015-06-24T11:57:40.107Z
Answers.Text: And obviously the pawn was forced forward in fact.
Answers.UserDisplayName: Martin Rattigan
Answers.ContentLicense: CC BY-SA 3.0
Answers.CreationDate: 2015-06-24T12:10:28.933Z
Answers.Text: @EDT.And also in the first position in fact. After 1. Ne5, Black is _forced_ to play 1. ... Kh7. These are _already_ instances of your "willy-nilly" defence.
Answers.UserDisplayName: Martin Rattigan
Answers.ContentLicense: CC BY-SA 3.0
Answers.CreationDate: 2015-06-24T12:28:35.263Z
Answers.Text: Sorry - brain malfunction again in the last two comments; just ignore.
Answers.UserDisplayName: Martin Rattigan
Answers.ContentLicense: CC BY-SA 3.0
Answers.CreationDate: 2015-06-24T18:21:43.063Z
Answers.Text: Let us [continue this discussion in chat](http://chat.stackexchange.com/rooms/25162/discussion-between-martin-rattigan-and-etd).
Answers.UserDisplayName: Martin Rattigan
Answers.ContentLicense: CC BY-SA 3.0
Answers.CreationDate: 2015-06-22T18:58:59.333Z
Answers.LastActivityDate: 2015-06-22T19:04:11.253Z
Answers.LastEditDate: 2015-06-22T19:04:11.253Z
Answers.UserDisplayName: ETD
Answers.Body: <p>For information I think the correct rule should be</p>
  
  <blockquote>
    <p>If a black pawn is  blockaded (by one of the white knights) on a square no further forward than the line a4–b6–c5–d4–e4–f5–g6–h4 and the blockading knight is protected by the other knight, then White can win the resulting endgame (and similarly in reverse for Black), no matter where the other pieces are placed.</p>
  </blockquote>
  
  <p>Müller and Lamprecht imply this version in Fundamental Chess Endings but unfortunately don't make it explicit, which means that if the rules governing Wikipedia content are strictly adhered to, this also can't be made explicit on the Wikipedia page (failing an alternative source).</p>
  
Answers.ContentLicense: CC BY-SA 3.0
Answers.CreationDate: 2015-07-07T15:57:40.237Z
Answers.LastActivityDate: 2015-07-07T15:57:40.237Z
Answers.UserDisplayName: Martin Rattigan
Body: <p>The current Wikipedia article on the two knights endgame states:</p>
  
  <blockquote>
    <p>For the position with White to move, Troitsky established that if a black pawn is securely blockaded (by one of the white knights) on a square no further forward than the line a4–b6–c5–d4–e4–f5–g6–h4, then White can win the resulting endgame (and similarly in reverse for Black), no matter where the other pieces are placed.</p>
  </blockquote>
  
  <p>I think the wording needs to be changed because various positions seem to me to be exceptions to the rule as stated. I'm having difficulty persuading the author of this, so perhaps it's me misunderstanding it.</p>
  
  <p>I thought, out of interest, that I might take a straw poll of how many people think that the draws below are adequately covered by the wording as it is and how many people think they area valid exceptions. </p>
  
  <p>Please leave a comment saying "covered" or "exception" if you read this. (If you think "covered" it would be helpful to me if you could say why, but you don't need to add any explanation if you don't want to.)</p>
  
  <p>I should mention here that, since this is a poll and I'm hoping for as many responses as possible, I won't actually accept any answers even if they are perfect.</p>
  
  <p>(I removed my first diagram because it was "cooked" as pointed out by GloriaVictis. The diagram was as shown in his answer.) </p>
  
  <p>2.</p>
  
  <pre><code>[fen "N6k/2p5/2N2K2/8/8/8/8/8 w - - 0 1"] 
  [White "Either"]
  [Black "to Move"]
  </code></pre>
  
  <p>3.</p>
  
  <pre><code>[fen "2N5/4p3/4N3/1k2K3/8/8/8/8 b - - 0 1"]
  [White "Black"]
  [Black "to Move"]
  </code></pre>
  
  <p>4.</p>
  
  <pre><code>[fen "7N/2p5/2N5/3K2k1/8/8/8/8 b - - 0 1"]
  [White "Black"]
  [Black "to Move"]
  </code></pre>
  
Comments.ContentLicense: CC BY-SA 3.0
Comments.CreationDate: 2015-06-24T22:26:02.100Z
Comments.Text: You can't be serious about the first position, that obviously is a draw...
Comments.UserDisplayName: user5649
Comments.ContentLicense: CC BY-SA 3.0
Comments.CreationDate: 2015-07-07T16:05:43.340Z
Comments.Text: I think it's an obvious exception to the rule as stated, but not everybody agrees - see the other replies. (Sorry about the delay in responding. I overlooked the comment.)
Comments.UserDisplayName: Martin Rattigan
Comments.ContentLicense: CC BY-SA 3.0
Comments.CreationDate: 2015-07-07T20:37:15.973Z
Comments.Text: By the way, feel free to leave an "exception" reply if that is what you mean - I'm a bit short of votes on this point.
Comments.UserDisplayName: Martin Rattigan
Tags: <endgame><knights>
Title: Wording of Troitsky line rule
ThreadText: # Wording of Troitsky line rule
  
  (Asked by: username_0 on 2015-06-22)
  
  The current Wikipedia article on the two knights endgame states:
  
  For the position with White to move, Troitsky established that if a black pawn is securely blockaded (by one of the white knights) on a square no further forward than the line a4–b6–c5–d4–e4–f5–g6–h4, then White can win the resulting endgame (and similarly in reverse for Black), no matter where the other pieces are placed.
  
  I think the wording needs to be changed because various positions seem to me to be exceptions to the rule as stated. I'm having difficulty persuading the author of this, so perhaps it's me misunderstanding it.
  I thought, out of interest, that I might take a straw poll of how many people think that the draws below are adequately covered by the wording as it is and how many people think they area valid exceptions. 
  Please leave a comment saying "covered" or "exception" if you read this. (If you think "covered" it would be helpful to me if you could say why, but you don't need to add any explanation if you don't want to.)
  I should mention here that, since this is a poll and I'm hoping for as many responses as possible, I won't actually accept any answers even if they are perfect.
  (I removed my first diagram because it was "cooked" as pointed out by username_2. The diagram was as shown in his answer.) 
  2.
  [fen "N6k/2p5/2N2K2/8/8/8/8/8 w - - 0 1"] 
  [White "Either"]
  [Black "to Move"]
  
  3.
  [fen "2N5/4p3/4N3/1k2K3/8/8/8/8 b - - 0 1"]
  [White "Black"]
  [Black "to Move"]
  
  4.
  [fen "7N/2p5/2N5/3K2k1/8/8/8/8 b - - 0 1"]
  [White "Black"]
  [Black "to Move"]
  
  **Tags:** endgame, knights
  
  > **Comments:**
  > **username_1**: You can't be serious about the first position, that obviously is a draw...  
  > **username_0**: I think it's an obvious exception to the rule as stated, but not everybody agrees - see the other replies. (Sorry about the delay in responding. I overlooked the comment.)  
  > **username_0**: By the way, feel free to leave an "exception" reply if that is what you mean - I'm a bit short of votes on this point.  
  
  ---
  
  ## 3 answers
  
  ### Answer by username_2 on 2015-06-22. Score: 4
  
  The key word in the rule is "securely". 
  Meaning, that there is nothing the opponent can do to lift the blockade. 
  In the posted position, white has to play 1. Ng6  - otherwise black will play 1. .. g5 and be beyond the Troitzky line - achieving draw immediately.
  Subsequently, the black king will march toward the pawn, starting with 1. .. Kc5 and force the g6 knight away, as white is not in time to defend it, neither with the king nor the other knight. Then, g5 will and draw will follow.
  Thus, the position appears to be covered by the rule in its current wording, as the pawn is not securely blockaded.
  EDIT - answering to the comment.
  4N3/6p1/8/8/1k5N/8/8/7K w - - 0 1
  
  1. Ng6 Kc5 2. Kg2 (2. Nc7 Kd6 3. Nb5+ (3. Ne8+ {pointless}) Ke6 {white is one move short of getting the other knight to e5} 4. Nd4+ Kf6 {white must move the knight away and g5 follows}) Kd5 Kg3 Ke6 4. Kg4 (4. Nf4+ Ke7 {white has to move the knight away and g5 follows}) (4. Nc7+ Kf7 {white is not in time to defend the knight, g5 will inevitably follow after a couple checks}) Kf7 {white cannot defend both knights}
  
  EDIT 2
  As for the later added positions, I believe they are all covered by username_3's answer.
  
  > **Comments:**
  > **username_0**: Well actually the king is in time to defend if the knight attacks. The knight needs 4 moves to attack and in the same 4 moves the king can move unhindered up th h file to protect.  
  > **username_2**: @MartinRattigan I'll add diagram & moves in a moment to demonstrate what I mean.  
  > **username_3**: @MartinRattigan, I'm not sure what line you have in mind exactly, but if you're saying the white king has time to head up and defend the g6 knight to maintain the blockade, that isn't so, e.g. `1.Ng6 Kc5 2.Kh2 Kd5 3.Kh3 Ke6 4.Kh4 Kf7` and one of the knights will be lost.  
  > **username_0**: For "knight needs 4 moves" in the above read "black king needs 4 moves". (Sorry, senility I think.)  
  > **username_0**: I agree that one of the knights will be lost in the process. So you have a valid point. This is the first vote of confidence so far. Thank you. I will add some extra positions.  
  > **username_0**: Sorry I seem to have lost the boards. Where is the documentation for producing these?  
  > **username_0**: By the way since this is a _poll_ rather than a question I won't actually accept any of the answers, but that is not to say that I find them unsatisfactory.  
  > **username_0**: Would you then say that the h4 pawn is not securely blockaded in this position? Black can force white to lift the blockade (and lose a knight).                                                                                   8/8/8/8/7p/1K5N/5N2/1k6 w - - 0 1  
  > **username_0**: Here is a diagram for the above comment.       [fen "8/8/8/8/7p/1K5N/5N2/1k6 w - - 0 1"]     [White "White"]     [Black "to Move and win"]  
  > **username_0**: Giving the diagram up for the time being  
  > **username_0**: I agree that the first position would never be regarded as an exception. to the wording. This position was a brain malfunction on my part. I had analysed a related position shortly before in which Kd5 was losing for black and somehow  assumed it still was. I looked no further than Kc5-c6.  
  
  ---
  
  ### Answer by username_3 on 2015-06-22. Score: 2
  
  I believe that username_2' answer addresses your first position very well, in that the pawn is not actually securely blockaded in that case; Black can force the further advance of the pawn.
  Your other positions are also susceptible to an insecure blockade, or are special in that, say, one of the knights is doomed to be lost, or else cannot participate in the play without capturing the pawn, yielding a draw in either case. For instance, position (4):
  [fen "7N/2p5/2N5/3K2k1/8/8/8/8 b - - 0 1"]
  
  1...Kf6 {The knight cannot be saved except by allowing the pawn to advance.} 2.Ne5 (2.Ke4 Kg7) c5 3.Nhf7
  
  So, one could insist that the wording cited in your question be strengthened to say something like, "the pawn is securely blockaded and neither of the knights faces imminent capture, or is forced to capture the pawn in order to participate, etc.." Ultimately, that is perhaps a matter of taste; I think most would instead say that these are clearly recognizable as special cases which the wording you cite need not attempt to address.
  
  > **Comments:**
  > **username_0**: Yes, except that the white king can prevent an attack on either knight in position 2. and black cannot force white to take the pawn.  
  > **username_0**: But again, thank you for your response. Another vote of confidence in the wording.  
  > **username_3**: Position 2 is what I had in mind when I wrote, "or is forced to capture the pawn in order to participate." For that position, Black doesn't need to do anything at all, and certainly doesn't need to bother attacking a knight. The white knight on a8 is trapped forever, unless White captures the pawn (draw), or the knight goes to b6 and is captured. Black can literally just move the king around willy-nilly and have a draw in that position.  
  > **username_0**: As white I wouldn't take the pawn unless I were playing against an EGTB. If white can immobilize the king on h1 or h8 then the pawn is forced forward and black loses.  
  > **username_3**: @MartinRattigan, I'm not sure how you're concluding Black loses even in that case. Say Black's king gets immobilized on h8 (by a white knight on f6 and king on f7), and so has to play `1...c5` freeing the a8 knight. Fine, but the pawn will also be able to advance to c4 in that scenario, and Black should be able to draw. But in any case, we're veering off the topic of your question.  
  > **username_0**: The second knight can deliver mate before the pawn queens if the king is immobilised before the pawn moves.  
  > **username_0**: But to stick to the topic, I don't think what we did discuss is adequately covered just by the phrase "securely blockaded".  
  > **username_0**: And actually my whole point is that this position _is_ a draw when the rule appears to say it should be a win for White.  
  > **username_3**: @MartinRattigan, I concur re: the immobilized king in Position 2 (though it's indeed moot since the stalemate in the corner can't be forced with only one knight participating beforehand). And I know your point is that the position is a draw; I'm less inclined to say that the rule says it should be a win for white. The way I think of that position is that, in essence, White only has one knight since the other is mechanically trapped out of play. ... (cont'd)  
  > **username_3**: (cont'd) ... At the end of the day, there is of course no cut-and-dried answer, since we're talking about textual interpretation. What I think mine and username_2' answers attempt to show is how the wording as given makes perfect sense when considered against the backdrop of an appropriate ambient chess-playing view of the scenarios. (E.g. I don't see position 2 as something that needs to be worried about for the reason I state above, that White really doesn't have two healthy knights to begin with in that position. All this is of course a matter of perspective.)  
  > **username_0**: The stalemate in the corner can't be forced from this position (it's drawn), but after 1.Ne5 it's conceivable that black could wander (willy-nilly) into a cornerable position (after all Karpov did exactly that against Topalov in 2001).  
  > **username_0**: username_3, you said "though it's indeed moot since the stalemate in the corner can't be forced with only one knight participating beforehand. I tried position 2. against Rybka and it blew it at the first attempt on move 2 (though not in the way I suggested). Game went 1. Ne5 Kg8 2. Ke6 c5 3. Nc4 Kg7.  
  > **username_0**: @EDT - Thought you might be interested in the last comment. (I just found out what the "@" symbol does.)  
  > **username_0**: @EDT. It lasted a bit longer on its second go, but it could take some time to get an example where it consistently uses your suggested defence. I don't believe the pawn was forced forward here either. 1. Ne5 Kg8 2. Nc4 Kh7 3. Ne3 Kh6 4. Ng4+ Kh5 5. Kf5 Kh4 6. Nf6 Kg3 7. Ke4 Kf2 8. Kd4 Kf3 9. Nd5 c5+ 10. Kc4 Kg4 11. Nc3 Kh4 12. Nb6 Kg4 13. Kd5 c4  
  > **username_0**: @EDT. By the way, the pawn past the Troitsky line where I stopped, but its OK with the black king  out of the a1 coirner.  
  > **username_0**: And obviously the pawn was forced forward in fact.  
  > **username_0**: @EDT.And also in the first position in fact. After 1. Ne5, Black is _forced_ to play 1. ... Kh7. These are _already_ instances of your "willy-nilly" defence.  
  > **username_0**: Sorry - brain malfunction again in the last two comments; just ignore.  
  > **username_0**: Let us [continue this discussion in chat](http://chat.stackexchange.com/rooms/25162/discussion-between-martin-rattigan-and-etd).  
  
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  ### Answer by username_0 on 2015-07-07. Score: 0
  
  For information I think the correct rule should be
  
  > If a black pawn is blockaded (by one of the white knights) on a square no further forward than the line a4–b6–c5–d4–e4–f5–g6–h4 and the blockading knight is protected by the other knight, then White can win the resulting endgame (and similarly in reverse for Black), no matter where the other pieces are placed.
  
  Müller and Lamprecht imply this version in Fundamental Chess Endings but unfortunately don't make it explicit, which means that if the rules governing Wikipedia content are strictly adhered to, this also can't be made explicit on the Wikipedia page (failing an alternative source).
  
  
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