Answers.Body: <p>Here's a #4 where White has just KNN and there are no Black units blocking Black king flights:</p>
  
  <pre><code>[Title "C. Barton; Family Herald 5 Nov 1859, no. 65"]
  [StartFlipped "0"]
  [fen "8/8/8/8/8/6K1/4p1N1/4N1k1 w - - 0 1"]
  
  1.Ne3 Kh1 2.Ng4 Kg1 3.Nf3+ Kh1 (3... Kf1 4.Ne3#/Nh2#) 4.Nf2#
  </code></pre>
  
  <p>Here's a #5 where White has just KNN and the play is a bit more interesting than in Barton's #4:</p>
  
  <pre><code>[Title "Otto Dehler; Denken und Raten 31 Dec 1934"]
  [StartFlipped "0"]
  [fen "8/1p6/8/8/3K4/N7/8/k1N5 w - - 0 1"]
  
  1.Kc3 b6 (1...b5 2.Kc2 b4 3.Kb3 bxa3 4.Kc2 a2 5.Nb3#) 2.Kc2 b5 3.Nb1 b4 4.Nd2 b3+ 5.Ndxb3#
  </code></pre>
  
Answers.ContentLicense: CC BY-SA 4.0
Answers.CreationDate: 2019-03-28T14:27:55.947Z
Answers.LastActivityDate: 2019-03-28T15:29:08.743Z
Answers.LastEditDate: 2019-03-28T15:29:08.743Z
Answers.UserDisplayName: Rosie F
Answers.Body: <p>To get the following position as a checkmate, the last move must be Nb3#.</p>
  
  <pre><code>[fen "8/8/8/8/8/1NN5/2K5/k7 b - - 0 2"]
  </code></pre>
  
  <p>Prior to Nb3#, black must have made a non-king move, so must have moved something to b3.  If it were anything other than a pawn, it could choose to avoid the b3 square, so it's not a forced win for white.  If it were a pawn on b4, it could capture the c3 knight, which is also not a forced win.  Thus black must have had a pawn on c4, and be forced to capture on b3 on black's previous move.</p>
  
  <p>So here's one such puzzle (<a href="https://lichess.org/analysis/standard/8/8/8/8/2pN4/2N5/1PK5/k7_w_-_-" rel="noreferrer">LiChess</a>):</p>
  
  <pre><code>[fen "8/8/8/8/2pN4/2N5/1PK5/k7 w - - 0 1"]
  </code></pre>
  
  <p>White to move and mate in 2.</p>
  
  <p>It's possible to move black's pawn back a bit, and give a slightly longer puzzle with the same idea:</p>
  
  <pre><code>[fen "8/8/2p5/8/7N/2N5/1PK5/k7 w - - 0 1"]
  </code></pre>
  
  <p>White to move and mate in 4.</p>
  
  <p>I haven't exhaustively checked all possible flips and rotations of the board (which makes more difference than I initially thought).  There's also a few possible mating patterns, but I expect the idea is going to be much the same in each case.</p>
  
Answers.ContentLicense: CC BY-SA 4.0
Answers.CreationDate: 2019-03-26T15:44:46.420Z
Answers.Text: "If it were anything other than a pawn, it could choose to avoid the b3 square,..." Is not quite correct. For instance (one of many counter examples): white Kc2, Nb3, Nc3, Nd4, black Ka1, Rb5.
Answers.UserDisplayName: user1583209
Answers.ContentLicense: CC BY-SA 4.0
Answers.CreationDate: 2019-03-28T14:27:30.607Z
Answers.Text: Your #4 is cooked: 1 b3, 1 Nf3 and 1 Nf5 all work. The play after 1 b3 and 1 Nf3 has further duals, but that after 1 Nf5 is sound.
Answers.UserDisplayName: Rosie F
Answers.ContentLicense: CC BY-SA 4.0
Answers.CreationDate: 2019-03-26T06:18:19.340Z
Answers.LastActivityDate: 2019-03-26T06:18:19.340Z
Answers.UserDisplayName: Rebecca J. Stones
Answers.Body: <p><a href="https://www.apronus.com/chess/puzzle/?p=08X8X2p5X8X7NX2N5X1PK5Xk7_w_-_-_0_1&amp;N=4&amp;w=rqsqpqq-aqfqrqw-aqfqiqw-aqpqiqq-aqpqsqw-iqrqpqq-iqoqiqq-iqoqsqw&amp;h=White%20to%20move%20and%20win%20by%20checkmate%20in%204%20moves&amp;m=9" rel="nofollow noreferrer">https://www.apronus.com/chess/puzzle/?p=08X8X2p5X8X7NX2N5X1PK5Xk7_w_-_-_0_1&amp;N=4&amp;w=rqsqpqq-aqfqrqw-aqfqiqw-aqpqiqq-aqpqsqw-iqrqpqq-iqoqiqq-iqoqsqw&amp;h=White%20to%20move%20and%20win%20by%20checkmate%20in%204%20moves&amp;m=9</a></p>
  
  <p>This is a real puzzle solving interface for one of the mate in 4 ideas given in another answer. There are many alternative solutions ending in 4.Nb3#</p>
  
Answers.ContentLicense: CC BY-SA 4.0
Answers.CreationDate: 2019-03-28T15:48:28.833Z
Answers.LastActivityDate: 2019-03-28T15:48:28.833Z
Answers.UserDisplayName: MichalRyszardWojcik
Answers.Body: <p>The mate in 4 from another answer can be presented as an interactive puzzle with this link
  <a href="https://www.apronus.com/chess/puzzle/?p=08X8X8X8X8X6K1X4p1N1X4N1k1_w_-_-_0_1&amp;N=4&amp;w=uqtqowd-uqtqoqp-uqtqoqf&amp;h=%3Ch1%3EMate%20in%204%3C%2Fh1%3EC.%20Barton%3B%20Family%20Herald%205%20Nov%201859%2C%20no.%2065&amp;m=9" rel="nofollow noreferrer">https://www.apronus.com/chess/puzzle/?p=08X8X8X8X8X6K1X4p1N1X4N1k1_w_-_-_0_1&amp;N=4&amp;w=uqtqowd-uqtqoqp-uqtqoqf&amp;h=%3Ch1%3EMate%20in%204%3C%2Fh1%3EC.%20Barton%3B%20Family%20Herald%205%20Nov%201859%2C%20no.%2065&amp;m=9</a></p>
  
  <p>While the mate in 5 is this <a href="https://www.apronus.com/chess/puzzle/?p=08X1p6X8X8X3K4XN7X8Xk1N5_w_-_-_0_1&amp;N=0&amp;w=owaqeqiqw-oqsqaqoqw&amp;h=%3Ch1%3EMate%20in%205%3C%2Fh1%3EOtto%20Dehler%3B%20Denken%20und%20Raten%2031%20Dec%201934&amp;m=9" rel="nofollow noreferrer">https://www.apronus.com/chess/puzzle/?p=08X1p6X8X8X3K4XN7X8Xk1N5_w_-_-_0_1&amp;N=0&amp;w=owaqeqiqw-oqsqaqoqw&amp;h=%3Ch1%3EMate%20in%205%3C%2Fh1%3EOtto%20Dehler%3B%20Denken%20und%20Raten%2031%20Dec%201934&amp;m=9</a></p>
  
Answers.ContentLicense: CC BY-SA 4.0
Answers.CreationDate: 2019-03-28T20:28:57.987Z
Answers.LastActivityDate: 2019-03-28T20:28:57.987Z
Answers.UserDisplayName: MichalRyszardWojcik
Body: <p>Does anyone know of any problems in which a KNN-K mate is forced in the end? It is fine if you make one yourself.</p>
  
Tags: <problems><knight-endgame>
Title: Looking for problems in which a KNN-K mate is forced
ThreadText: # Looking for problems in which a KNN-K mate is forced
  
  (Asked by: username_0 on 2019-03-26)
  
  Does anyone know of any problems in which a KNN-K mate is forced in the end? It is fine if you make one yourself.
  
  **Tags:** problems, knight-endgame
  
  
  ---
  
  ## 4 answers
  
  ### Answer by username_1 on 2019-03-28. Score: 4 | Accepted answer
  
  Here's a #4 where White has just KNN and there are no Black units blocking Black king flights:
  [Title "C. Barton; Family Herald 5 Nov 1859, no. 65"]
  [StartFlipped "0"]
  [fen "8/8/8/8/8/6K1/4p1N1/4N1k1 w - - 0 1"]
  
  1.Ne3 Kh1 2.Ng4 Kg1 3.Nf3+ Kh1 (3... Kf1 4.Ne3#/Nh2#) 4.Nf2#
  
  Here's a #5 where White has just KNN and the play is a bit more interesting than in Barton's #4:
  [Title "Otto Dehler; Denken und Raten 31 Dec 1934"]
  [StartFlipped "0"]
  [fen "8/1p6/8/8/3K4/N7/8/k1N5 w - - 0 1"]
  
  1.Kc3 b6 (1...b5 2.Kc2 b4 3.Kb3 bxa3 4.Kc2 a2 5.Nb3#) 2.Kc2 b5 3.Nb1 b4 4.Nd2 b3+ 5.Ndxb3#
  
  
  ---
  
  ### Answer by username_2 on 2019-03-26. Score: 6
  
  To get the following position as a checkmate, the last move must be Nb3#.
  [fen "8/8/8/8/8/1NN5/2K5/k7 b - - 0 2"]
  
  Prior to Nb3#, black must have made a non-king move, so must have moved something to b3.  If it were anything other than a pawn, it could choose to avoid the b3 square, so it's not a forced win for white.  If it were a pawn on b4, it could capture the c3 knight, which is also not a forced win.  Thus black must have had a pawn on c4, and be forced to capture on b3 on black's previous move.
  So here's one such puzzle (LiChess):
  [fen "8/8/8/8/2pN4/2N5/1PK5/k7 w - - 0 1"]
  
  White to move and mate in 2.
  It's possible to move black's pawn back a bit, and give a slightly longer puzzle with the same idea:
  [fen "8/8/2p5/8/7N/2N5/1PK5/k7 w - - 0 1"]
  
  White to move and mate in 4.
  I haven't exhaustively checked all possible flips and rotations of the board (which makes more difference than I initially thought).  There's also a few possible mating patterns, but I expect the idea is going to be much the same in each case.
  
  > **Comments:**
  > **username_3**: "If it were anything other than a pawn, it could choose to avoid the b3 square,..." Is not quite correct. For instance (one of many counter examples): white Kc2, Nb3, Nc3, Nd4, black Ka1, Rb5.  
  > **username_1**: Your #4 is cooked: 1 b3, 1 Nf3 and 1 Nf5 all work. The play after 1 b3 and 1 Nf3 has further duals, but that after 1 Nf5 is sound.  
  
  ---
  
  ### Answer by username_4 on 2019-03-28. Score: 1
  
  <https://www.apronus.com/chess/puzzle/?p=08X8X2p5X8X7NX2N5X1PK5Xk7_w_-_-_0_1&N=4&w=rqsqpqq-aqfqrqw-aqfqiqw-aqpqiqq-aqpqsqw-iqrqpqq-iqoqiqq-iqoqsqw&h=White%20to%20move%20and%20win%20by%20checkmate%20in%204%20moves&m=9>
  
  This is a real puzzle solving interface for one of the mate in 4 ideas given in another answer. There are many alternative solutions ending in 4.Nb3#
  
  
  ---
  
  ### Answer by username_4 on 2019-03-28. Score: 1
  
  The mate in 4 from another answer can be presented as an interactive puzzle with this link
  <https://www.apronus.com/chess/puzzle/?p=08X8X8X8X8X6K1X4p1N1X4N1k1_w_-_-_0_1&N=4&w=uqtqowd-uqtqoqp-uqtqoqf&h=%3Ch1%3EMate%20in%204%3C%2Fh1%3EC.%20Barton%3B%20Family%20Herald%205%20Nov%201859%2C%20no.%2065&m=9>
  
  While the mate in 5 is this <https://www.apronus.com/chess/puzzle/?p=08X1p6X8X8X3K4XN7X8Xk1N5_w_-_-_0_1&N=0&w=owaqeqiqw-oqsqaqoqw&h=%3Ch1%3EMate%20in%205%3C%2Fh1%3EOtto%20Dehler%3B%20Denken%20und%20Raten%2031%20Dec%201934&m=9>
  
  
  ---
  
  