2

While this asks for a reason/any reason in general, I wish to make a list of numerous posssible unique reasons.

I already have an exhaustive list of my own. Are there any more possible reasons out there? Can any of these be generalized further? If you can come up with another reason, please give an example.


My List-Practical Game Examples Are Used If Possible

To give checkmate

[Title "William Strum-John McManus, Eastern Open, Washington, District hof Columbia USA, 12/29/1997"]
[FEN ""]
[startply "78"]

1. e4 e5 2. f4 exf4 3. Nf3 Be7 4. Bc4 Bh4+ 5. Kf1 Nh6 6. Nc3 O-O 7. d4 Ng4 8. Nxh4 Qxh4 9. Qe2 Nc6 10. Bxf4 Nxd4 11. Qd2 Qf6 12. Nd5 Qd8 13. Qxd4 d6 14. h3 c6 15. hxg4 cxd5 16. Qxd5 Be6 17. Qh5 Bxc4+ 18. Kf2 h6 19. g5 Qb6+ 20. Be3 Qxb2 21. Rac1 Kh7 22. gxh6 g6 23. Qd1 Qf6+ 24. Qf3 Qxf3+ 25. gxf3 Rfe8 26. a3 d5 27. exd5 Bxd5 28. Rcd1 Be6 29. c3 b6 30. Rh4 Rac8 31. Rf1 f6 32. f4 Rf8 33. Kg3 Rc4 34. Bd4 g5 35. fxg5 fxg5 36. Re1 Bg4 37. Re7+ Kg6 38. h7 Rf3+ 39. Kxg4 Rfxc3 40. h8=N#

To avoid checkmate

[Title "Kaan Kucuksari-Alexander Betaneli, Rilton Cup 2016/17, Stockholm Sweden, 1/4/2017"]
[FEN ""]
[startply "142"]

1. d4 d5 2. Nf3 Nf6 3. c4 e6 4. g3 dxc4 5. Bg2 Bb4+ 6. Bd2 a5 7. O-O O-O 8. Qc2 Nc6 9.  Qxc4 Qd5 10. Qd3 Qf5 11. Qxf5 exf5 12. a3 Bxd2 13. Nbxd2 Be6 14. e3 Bd5 15. Rac1 Rfd8 16. Rfd1 a4 17. Ne5 Bxg2 18. Kxg2 Nxe5 19. dxe5 Nd5 20. e4 fxe4 21. Nxe4 Kf8 22. Kf3 c6 23. Nd6 Rd7 24. Ke4 Rad8 25. Rd4 Nf6+ 26. Ke3 Ne8 27. Nf5 g6 28. Rxd7 Rxd7 29. Nd4 Re7 30. f4 f6 31. Nf3 Nd6 32. Kd4 Nf5+ 33. Kc5 Rd7 34. exf6 Rd5+ 35. Kb6 Rb5+ 36. Kc7 Ne3 37. Re1 Nd5+ 38. Kd6 Nxf6 39. Re6 Ne8+ 40. Kd7 Rd5+ 41. Kc8 Nd6+ 42. Kc7 Nf7 43. Re2 Rd3 44. Ne5 Nxe5 45. fxe5 Rb3 46. Kd7 Rd3+ 47. Ke6 b5 48. Rf2+ Kg8 49. Rc2 Rb3 50. Kd6 b4 51. axb4 Rxb4 52. e6 Kf8 53. Rxc6 Rd4+ 54. Ke5 Rd2 55. Rc8+ Ke7 56. Rc7+ Ke8 57. Rxh7 Rxb2 58. Kf6 Rf2+ 59. Kxg6 a3 60. h4 Rf3 61. g4 Rf4 62. g5 Ra4 63. Rd7 a2 64. Rd1 a1=Q 65. Rxa1 Rxa1 66. h5 Ke7 67. h6 Kxe6 68. h7 Ra8 69. Kh6 Kf5 70. g6 Kf6 71. g7 Ra1 72. g8=N+ Kf7 73. h8=N+ Kxg8 74. Ng6 Rg1 75. Ne5 Kf8 76. Kh5 Ke7 77. Ng4 Ke6 78. Kg5 Rf1 79. Kg6 Rf8 80. Nh6 Ke5 81. Kg5 Ke4 82. Kg4 Rf1 83. Kg5 Rh1 84. Nf7 Kd5 85. Kf6 Rf1+ 86. Kg6 Ke6 87. Ng5+ Ke7 88. Kh5 Kf6 89. Ne4+ Ke5 90. Ng3 Rf4 91. Kg5 Rf8 92. Kg4 Rf4+ 93. Kg5 Rf7 94. Kg4 Rf8 95. Nh5 Rh8 96. Ng3 Rb8 97. Nh5 Rb4+ 98. Kg5 Ra4 99. Ng3 Rc4 100. Nh5 Rc8 101. Kg4 Rg8+ 102. Kf3 Rg6 103. Ng3 Rg5 104. Ne2 Rf5+ 105. Ke3 Rh5 106. Kf3 Rh2 107. Ng3 Ra2 108. Ne2 Ra3+ 109. Kg4 Rb3 110. Ng3 Re3 111. Nf5 Re4+ 112. Kg5 Rf4 113. Ng3 Rb4 114. Nf5 Rb8 115. Nh6 Ke4 116. Nf7 Rb5+ 117. Kf6 Kf4 118. Nd6 Re5 119. Nf7 Rd5 120. Ke6

To create a potential/have a mating threat

[Title "Vladimir Eduardovich Akopia-Sergey Karjakin, 4th FIDE Grand Prix, Nalchik Russia, 4/21/2009 "]
[FEN ""]
[startply "140"]

1. e4 c5 2. Nf3 d6 3. d4 cxd4 4. Nxd4 Nf6 5. Nc3 a6 6. Be3 Ng4 7. Bg5 h6 8. Bh4 g5 9. Bg3 Bg7 10. h3 Nf6 11. Qf3 Qb6 12. O-O-O Nc6 13. Nxc6 Qxc6 14. Be2 Nd7 15. Nd5 Ne5 16. Qa3 b5 17. h4 Be6 18. hxg5 Rc8 19. Rd2 hxg5 20. Rxh8+ Bxh8 21. Qe3 Nc4 22. Bxc4 bxc4 23. c3 f6 24. Qa7 Bd7 25. f3 Bg7 26. Nb6 Rd8 27. Qxa6 Be6 28. Qa7 Kf7 29. Nd5 Bxd5 30. exd5 Qa8 31. Qc7 Rc8 32. Qd7 Rh8 33. Qe6+ Kf8 34. a3 Rh1+ 35. Rd1 Rxd1+ 36. Kxd1 Qa4+ 37. Kd2 Qb3 38. Kc1 Qb6 39. Be1 Qg1 40. g4 Qf1 41. Qe4 Ke8 42. Kd2 Kd8 43. Qe2 Qh1 44. Kc2 f5 45. gxf5 Qh3 46. Qxc4 Qxf3 47. Qd3 Qg2+ 48. Kb3 g4 49. a4 Be5 50. a5 Qg1 51. Qb5 Qxe1 52. a6 Qa1 53. Qb8+ Kd7 54. Qb5+ Kd8 55. Qb6+ Kc8 56. Qc6+ Kd8 57. Qa8+ Kd7 58. Qc6+ Kd8 59. Qa8+ Kd7 60. Qb7+ Kd8 61. Qb8+ Kd7 62. a7 Qd1+ 63. Kb4 Bxc3+ 64. Kxc3 Qc1+ 65. Kb3 Qd1+ 66. Kb4 Qe1+ 67. Kb5 Qf1+ 68. Kb6 Qg1+ 69. Ka6 Qa1+ 70. Kb7 Qc1 71. a8=N

To give a double check/checkmate that wouldn’t work otherwise due to the discovered attacker being attacked.

[Title "Avetik Grigoryan-Tigran L. Petrosian, Lake Sevan GM, Martuni Armenia, 7/11/19"]
[FEN ""]
[startply "99"]

1. Nf3 d5 2. d4 c6 3. c4 Nf6 4. e3 e6 5. Bd3 Nbd7 6. Nbd2 dxc4 7. Nxc4 c5 8. O-O Be7 9. e4 cxd4 10. e5 Nd5 11. Nxd4 Nc5 12. Bc2 O-O 13. a3 a5 14. Qg4 f5 15. Qg3 Qe8 16. Bg5 a4 17. Bxe7 Qxe7 18. Rfd1 Ne4 19. Bxe4 fxe4  20. Nd6 e3 21. fxe3 Bd7 22. Rac1 Bc6 23. h3 h6 24. Kh2 Kh7 25. Rf1 Nb6 26. Nxc6 bxc6 27. Rxf8 Rxf8 28. Rxc6 Nd5 29. Qg4 Nxe3 30. Qe4+ Nf5 31. g4 Qh4 32. gxf5 Qf2+ 33. Qg2 Qf4+ 34. Kh1 exf5 35. e6 Qe5 36.Nc4 Qe1+ 37.Kh2 Rf6 38.Qg1 Qe4 39.Qg2 Qf4+ 40.Qg3 Qe4 41.Rc5 Rxe6 42.Qf2 f4 43. h4 f3 44.h5 Qg4 45.Qc2+ Re4 46.Nd6 f2 47. Rf5 Qg1+ 48. Kh3 Qg4+ 49. Kh2 Re2 50. Qd3 f1=N+

To give a check and gain a tempo

[Title "Hikaru Nakamura-Vladimir Kramnik, Chess Olympiad, Istanbul Turkey, 9/6/19"]
[FEN ""]
[startply "122"]

1. Nf3 Nf6 2. g3 g6 3. Bg2 Bg7 4. c4 c6 5. d4 d5 6. cxd5 cxd5 7. Nc3 Ne4 8. Qb3 Nxc3 9. bxc3 O-O 10. Nd2 e6 11. e4 Nc6 12. O-O Na5 13.  Qd1 Qc7 14. Qf3 b6 15. Ba3 Rd8 16. e5 Ba6 17. Rfe1 Rac8 18. Bb4 Bh6 19. Qd1 Nc6 20. Ba3 Na5 21. Bb4 Nc6 22. Ba3 Na5 23. Nb1 b5 24. h4 Nc6 25. Bc5 Qb8 26. Qe2 Na5 27. Nd2 Rxc5 28. dxc5 Qc8 29. Nf3 Qxc5 30. Nh2 Bg7 31. h5 g5 32. h6 Bxh6 33. Qh5 Bg7 34. Qxg5 Nc6 35. Ng4 Qe7 36. Qxe7 Nxe7n37. a4 d4 38. axb5 Bxb5 39. Rxa7 d3 40. Rxe7 d2 41. Rd1 Be2 42. Ne3 Bxe5 43. c4 h5 44. Ra7 h4 45. Ra2 Bxd1 46. Nxd1 hxg3 47. fxg3 Bxg3 48. c5 f5 49. Ra7 e5 50. c6 e4 51. Bh3 Rc8 52. Ra6 Rf8 53. Ra5 f4 54. Kf1 e3 55. Ke2 Rf6 56. Ra8+ Kg7 57. Ra7+ Rf7 58. Rb7 Kf6 59. Kf3 Re7 60. Rxe7 Kxe7 61. c7 e2 62. c8=N+ Kf6 63. Kxe2 Ke5 64. Nb6 Kd4 65. Bg2 Be1 66. Nd5 Ke5 67. Nb4 Bh4 68. Nd3+ Kf5 69. Kxd2 Kg4 70. Ke2 Bf6 71. N1f2+ Kg3 72. Bf3 Bd8 73. Ne4+ Kh4 74. Ne5 Bc7 75. Ng6+ Kh3 76. Ne7 Bd8 77. Nf5 Bb6 78. Kf1 Kh2 79. Bg4 f3 80. Nh4

To gain a perputual check

[Title "Niclas Huschenbeth-Robin Swinkels, Bundesliga 2007/08, Godesberg Germany, 2/9/2008"]
[FEN ""]
[startply "64"]

1. e4 c5 2. Nf3 d6 3. d4 cxd4 4. Nxd4 Nf6 5. Nc3 Nc6 6. Bg5 e6 7. Qd2 a6 8. O-O-O Bd7 9. f3 Be7 10. Be3 h5 11. Kb1 Qc7 12. Nxc6 Bxc6 13. Ne2 d5 14. e5 Nd7 15. f4 Bb5 16. g3 g6 17. Bg2 Bxe2 18. Qxe2 b5 19. h3 Bc5 20. Bxc5 Qxc5 21. g4 Nb6 22. b3 Rb8 23. Qd2 Nc4 24. bxc4 bxc4+ 25. Ka1 c3 26. Qd4 Qa3 27. Rb1 Rb2 28. Bxd5 exd5 29. Qxd5 O-O 30. e6 Rfb8 31. exf7+ Kg7 32. Qe5+ Kh7 33. f8=N+ Rxf8 34. Qc7+ Kh8 35. Qe5+ Kh7 36. Qc7+

To stop a perputual check

[Title "Anatoly Karpov-Jan Timman, SWIFT Tournament 1st, Brussels Belgium, 3/24/1986"]
[FEN ""]
[startply "172"]

1. Nf3 Nf6 2. c4 b6 3. g3 c5 4. Bg2 Bb7 5. O-O g6 6. d4 Bg7 7. Nc3 Ne4 8. Nxe4 Bxe4 9. d5 e5 10. Qb3 O-O 11. Bh3 Bxf3 12. Qxf3 f5 13. e4 f4 14. Qd1 d6 15. Bd2 a5 16. Qa4 Bh6 17. Rac1 Bg5 18. Rc2 Kh8 19. a3 Ra7 20. Be1 Qe8 21. Qxe8 Rxe8 22. Bd2 Na6 23. Rb1 Rf8 24. Rc3 Kg7 25. Bg4 Raf7 26. Rb3 Rb8 27. Bd1 h5 28. h4 Bh6 29. g4 hxg4 30. Bxg4 Kf6 31. Kf1 Rfb7 32. Ke1 Bf8 33. Rh3 Rh7 34. Ke2 Be7 35. h5 gxh5 36. Rxh5 Rxh5 37. Bxh5 Rg8 38. Bf3 Rh8 39. Bg4 Nc7 40. Bd7 Kf7 41. Ra1 Bg5 42. Bc3 Ke7 43. Bf5 Bf6 44. Rd1 Ra8 45. Kd3 Rh8 46. Be1 Ra8 47. Bd2 Rh8 48. Rc1 Ra8 49. Rc3 Rh8 50. Rb3 Na8 51. Ke2 Bg5 52. Be1 Rh1 53. Bc8 Bh4 54. Bd2 Rh2 55. Be1 Rh1 56. Bb7 Nc7 57. Bc6 Kd8 58. Bd2 Rh2 59. Be1 Rh1 60. Ba4 Kc8 61. Bc3 Rh2 62. Rxb6 Rxf2+ 63. Kd3 Rf3+ 64. Kc2 Rg3 65. Rxd6 f3 66. Rh6 f2 67. Rh8+ Kb7 68. Bc6+ Ka6 69. Rf8 Rg8 70. Rf3 Rg3 71. Rf5 Rg5 72. Rf7 Rg7 73. Rf3 Rg3 74. Rf5 Rg5 75. Rf8 Rg8 76. Rf7 Rg7 77. Rxg7 f1=Q 78. Rxc7 Qxc4 79. a4 Qxe4+ 80. Kb3 Be1 81. d6 Qh4 82. Bb5+ Kb6 83. Rc6+ Kb7 84. d7 Bxc3 85. bxc3 c4+ 86. Rxc4 Qe1 87. d8=N+ Ka7 88. Rc7+ Kb8 89. Rd7 Qb1+ 90. Kc4 Qf1+ 91. Kd5 Qf3+ 92. Kd6 Qf8+ 93. Ke6 Qh6+ 94. Kxe5 Qe3+ 95. Kd6 Qf4+ 96. Kc5 Qe3+ 97. Kc4 Kc8 98. Nf7 Qe4+ 99. Kc5 Qe3+ 100. Kc6 Qxc3+ 101. Kb6 Qe3+ 102. Ka6 Qe6+ 103. Nd6+ Kb8 104. Rd8+ Kc7 105. Rc8+

To guard an otherwise unguardable square (whether to protect a piece, stop a checkmate threat, or to take away a flight square away from the enemy king)

[Title "Michael Adams-Anthony Miles, Tilburg, Tilburg Netherlands, 11/17/1993"]
[FEN ""]
[startply "179"]

1.e4 c5 2.Nf3 d6 3.d4 cxd4 4.Nxd4 Nf6 5.Nc3 g6 6.Be2 Bg7 7.O-O O-O 8.Bg5 Nc6 9.Nb3 a6 10.Re1 b5 11.Bf1 h6 12.Bh4 e6 13.Qd2 Qc7 14.Rad1 Rd8 15.f4 Bb7 16.a3 Rac8 17.f5 Ne5 18.fxe6 fxe6 19.Nd4 Qe7 20.Nf3 g5 21.Bf2 Nxf3+ 22.gxf3 Nh5 23.Bd4 Bxd4+ 24.Qxd4 Qf8 25.Qe3 Rc7 26.Ne2 Rf7 27.Bh3 Bc8 28.Rf1 Kh8 29.Bg4 Nf4 30.Nxf4 Rxf4 31.Rd2 Qf7 32.Bh3 Rf8 33.Bg2 Bb7 34.Rfd1 d5 35.h3 Kg8 36.c3 Qg7 37.Qb6 Qf7 38.Qe3 Rf6 39.e5 Rf5 40.Rd4 Qg7 41.Re1 Bc6 42.h4 Be8 43.Rg4 Bh5 44.Rg3 g4 45.Qd4 Kh8 46.fxg4 Rf4 47.Qe3 Rxg4 48.Rxg4 Bxg4 49.Rf1 Bf5 50.Kh2 Kh7 51.Qg3. Qxg3+ 52.Kxg3 Rg8+ 53.Kf2 Rg4 54.h5 Rg5 55.Bf3 Bc2 56.Re1 Kh8 57.Re3 Bh7 58.Ke2 Kg7 59.Kd2 Kf8 60.Re2 Ke8 61.Rg2 Rxe5 62.Rg7 Be4 63.Bxe4 Rxe4 64.Rh7 Rh4 65.Rxh6 Ke7 66.Rh8 Kf6 67.h6 Ke5 68.h7 a5 69.Rb8 Rxh7 70.Rxb5 Ke4 71.Rxa5 Rh2+ 72.Kc1 Kd3 73.Kb1 Rh1+ 74.Ka2 Kc2 75.a4 Rh8 76.Ra6 e5 77.Re6 e4 78.Ka3 Rb8 79.b4 Kxc3 80.b5 Rd8 81.b6 d4 82.Rxe4 d3 83.Re1 d2 84.Rd1 Rd3 85.b7 Kc2+ 86.Ka2 Rd8 87.Rxd2+ Kxd2 88.a5 Kc2 89.a6 Rd6 90.b8=N Rd5 91.Ka3 Kc3 92.Ka4 Kc4 93.Nc6 Rd1 94.Na5+ Kc5 95.Nb3+ Kb6 96.a7 Kxa7 97.Kb4 Kb6 98.Kc3 Rh1 99.Nd4 Rh4 100.Nb3 Kc6 101.Nd4+ Kd5 102.Nb3 Rc4+ 103.Kd3 Ra4 104.Kc3 Ra8v105.Kd3 Rh8 106.Kc3 Rh7 107.Kb4 Rh3 108.Na5 Rh4+ 109.Kb5 Kd4 110.Nc6+ Kd5 111.Nb4+ Kd6 112.Na6 Rh5+ 113.Kb6 Rd5 114.Nc7 Rd1 115.Nb5+ Kd5 116.Nc7+ Ke5 117.Nb5 Rc1 118.Nc7 Kd4 119.Nb5+ Kd5 120.Nc7+ Kd6 121.Nb5+ Kd7 122.Nd4

To give a fork

[Title "George Alcock MacDonnell-Henry Edward Bird, London England, 1874"]
[FEN ""]
[startply "43"]

1. e4 e5 2. f4 exf4 3. Nf3 g5 4. h4 g4 5. Ne5 h5 6. Bc4 Nh6 7. d4 d6 8. Nd3 f3 9. g3 f5 10. Nc3 fxe4 11. Nxe4 Nf5 12. Kf2 Be7 13. Nf4 Rh7 14. Ng6 d5 15. Nxe7 dxe4 16. Nd5 Be6 17. Bg5 Bxd5 18. Bxd8 e3+ 19. Kg1 Bxc4 20. Bg5 f2+ 21. Kh2 e2 22. Qd2 f1=N+ 23. Rhxf1 exf1=N+ 24. Rxf1 Bxf1 25. Qe1+ Ne7 26. Qxf1 Nbc6 27. d5 Rf7 28. Qc4 Ne5 29. Qxc7 Nf3+ 30. Kg2 Rc8 31. Qa5 Rxc2+ 32. Kf1 Nxg5+ 33. Ke1 Nf3+ 34. Kd1 Rd2+ 35. Kc1 Nxd5 36. a3 Rc7+ 37.Kb1 Nc3+ 38.bxc3 Re7

To avoid a fork

[Title "Vladlen Yakovlevich Zurakhov-Alexander Koblents, URS-ch sf, Tbilisi USSR, 1956"]
[FEN ""]
[startply "112"]

1.e4 e6 2.d4 d5 3.Nc3 Nf6 4.Bg5 dxe4 5.Nxe4 Be7 6.Bxf6 gxf6 7.Nf3 b6 8. Bc4 Bb7 9.Qe2 c6 10.O-O Nd7 11.a4 f5 12.Ng3 Kf8 13.Bxe6 fxe6 14.Qxe6 Nf6 15.Nxf5 Bc8 16.Qe5 Bxf5 17.Qxf5 Qd5. 18.Qf4 Rg8 19.Rae1 Rg4 20.Qh6+ Kg8 21.Rxe7 Qxf3 22.g3 Rg6 23.Qh3 Qg4 24.Qxg4 Rxg4 25.c3 Re4 26.Rxe4 Nxe4 27. Re1 Re8 28.f3 Nd6 29.Rxe8+ Nxe8 30.Kf2 Nd6 31.b3 b5 32.Ke3 bxa4 33.bxa4 Nc4+ 34.Ke4 Kf7 35.d5 c5 36.f4 a5 37.f5 Nb6 38.d6 Ke8 39.f6 Kf7 40.Ke5 Nd7+ 41.Kd5 Kxf6 42.g4 c4 43.Kc6 Ke6. 44.g5 Nf8 45.h4 Nd7 46.h5 Ne5+ 47. Kc7 Kf5 48.Kb6 Ke6 49.Kxa5 Kxd6 50.Kb6 Nd7+ 51.Kb5 Kc7 52.Kxc4 Ne5+ 53. Kd5 Nf3 54.g6 hxg6 55.hxg6 Nh4 56.g7 Nf5 57.g8=N Kb6 58.Kc4 Ne3+ 59.Kb3 Nd5 60.c4 Nc7 61.Nf6 Ne6 62.Ne4 Nc7 63.Nf2 Ne6 64.Nd3 Nd4+ 65.Kc3 Ne2+ 66.Kb4 Nd4 67.c5+ Ka6 68.Kc4 Nf5 69.Kd5 Kb7 70.Nb4 Ne3+ 71.Kd4 Nf5+ 72. Kc4 Ne3+ 73.Kb5 Kc7 74.a5 Nf5 75.Nd5+ Kb7 76.c6+ Ka7 77.c7 Kb7 78.a6+ Ka7 79.c8=N+ Kb8 80.Kb6

To avoid a discovered attack on the newly born piece

[Title "Vladimir Antoshin-Vladimir Simagin, Moscow USSR, 1952"]
[FEN ""]
[startply "88"]

1.Nf3 Nf6 2.b3 g6 3.Bb2 Bg7 4.g3 O-O 5.Bg2 a5 6.O-O d6 7.d4 a4 8.c4 Nbd7 9.Qc2 c5 10.e4 cxd4 11.Nxd4 Qb6 12.Nb5 axb3 13.axb3 Rxa1 14.Bxa1 Nc5 15.Bd4 e5 16.Be3 Ng4 17.Bg5 f6 18.Bc1 f5 19.h3 Nf6 20.exf5 Bxf5 21.Qd1 Bxb1 22.Be3 Ba2 23.Qc2 Bxb3 24.Qxb3 Nxb3 25.Bxb6 Nd2 26.Rc1 Bh6 27.Rc2 Nfe4 28.Nc3 Nxc3 29.Rxc3 e4 30.Bc7 Rc8 31.Bxd6 b5 32.c5 b4 33.Rc2 b3 34.Rb2 Kf7 35.h4 Ra8 36.c6 Nc4 37.Bxe4 Ra1+ 38.Kg2 Nxb2 39.Bd5+ Ke8 40.Bxb3 Rc1 41.Bd5 Nc4 42.Bb8 Na5 43.c7 Ke7 44.Bf3 Nc4 45.c8=N+ Kf8 46.Nd6 Ne5 47.Ne4 Nxf3 48.Kxf3 Bg7 49.Bf4 Rc2 50.Ng5 Kg8 51.Be3 Bf6 52.Kg2 Be7 53.Kf3 Bc5 54.Bxc5 Rxc5m55.Kg2 Rc3 56.Nh3 Ra3 57.Ng1 Kg7m58.Nf3 Kf6 59.Ng5 h6 60.Nh3 Kf5 61.Nf4 Rb3 62.Nh3 Ke4 63.Nf4 Rb6 64.Nh3 Rf6 65.Ng1 Kd3 66.Nf3 Rd6 67.Ne5+ Ke2 68.Nf3 Rd5 69.Ng1+ Kd3 70.Nh3 Ke4 71.Nf4 Rd6 72.Nh3 Rb6 73.Nf4 g5 74.hxg5 hxg5 75.Nh3 g4 76. Nf4 Rb1 77. Ng6 Re1 78.Nf4 Rd1 79.Ng6 Ra1 80.Nf4 Ra2 81.Ng6 Kd4m82.Nf4 Ra6 83.Ne2+ Kd3 84.Nf4+ Kc3 85.Nd5+ Kd2 86.f3 Rd6 87.Nf4 Ke3 88.fxg4 Rd2+ 89.Kh3 Kf3

To create a discovered attack

 [Title "Frank James Marshall-William Ewart Napier, Brooklyn, 1898"]
 [FEN ""]
 [startply "98"]

1.d4 d5 2.c4 e5 3.cxd5 Qxd5 4.Nf3 exd4 5.Nxd4 Bc5 6.e3 Bxd4 7.exd4 Nc6 8.Be3 Nf6 9.Nc3 Qa5 10.Bb5 Bd7 11.O-O O-O 12.a3 Ne4 13.Nxe4 Qxb5 14.Nc5 Rad8 15.Qd2 Bc8 16.Rac1 b6 17.Ne4 Nxd4 18.Bxd4 c5 19.Qg5 Rxd4 20.Nf6+ Kh8 21.f4 Qxb2 22.Rce1 Rd2 23.Ne4 f6 24.Qg3 Qd4+ 25.Nf2 Qd8 26.Re3 Bf5 27.Rfe1 Rd7 28.Qf3 Rg8 29.g4 Bg6 30.f5 Bf7 31.h4 c4 32.Qh3 Re8 33.Rxe8+ Bxe8 34.Qe3 Bf7 35.g5 Rd5 36.Ng4 fxg5 37.Ne5 Bg8 38.hxg5 Rd2 39.g6 h6 40.Nf7+ Bxf7 41.gxf7 Kh7 42.Qg3 Rd6 43.Qg4 c3 44.Re8 Rd1+ 45.Kf2 Rd2+ 46.Ke1 Rd1+ 47.Qxd1. Qh4+ 48.Kf1 Qh1+ 49.Kf2 Qxd1 50.f8=N+ Kg8 51.Ng6+ Kf7 52.Rf8#

To win a piece without a fork

[Title "Suat Atalik-Anthony Miles, Iraklion Greece, 1993"]
[FEN ""]
[startply "59"]

1.d4 Nf6 2.c4 g6 3.Nc3 Bg7 4.e4 d6 5.f3 O-O 6.Be3 c5 7.Nge2 Nc6 8.Qd2 e6 9.Rd1 b6 10.Bg5 Ba6 11.d5 Ne5 12.b3 h6 13.Be3 exd5 14.Nxd5 Nxd5 15.Qxd5 b5 16.cxb5 Bxb5 17.Nc1 Bc6 18.Qd2 f5 19.Qxd6 Qe8 20.Qxc5 fxe4 21.f4 Nd3+ 22.Nxd3 exd3 23.Kf2 Rc8 24.Qc4+ Kh8 25.Qxd3 g5 26.Rc1 Rd8 27.Qe2 gxf4 28.Bc5 f3 29.Qxe8 fxg2+ 30.Bxf8 gxh1=N+ 

To gain a skewer

[FEN "5Q2/8/8/4p3/p1k1P3/B1p1K3/2PpP3/4r3 b - - 0 1"]

1. d1=N+ Kf3 2. Rf1+ Kg4 3. Rxf8

To avoid a skewer (pretending that the example doesn’t end in mate)

[Title "Gawain Jones-Danny Raznikov, Isle of Man Masters, Douglas Isle of Man, 10/12/2014"]
[FEN ""]
[startply "136"]

1. e4 c5 2. Nf3 d6 3. d4 cxd4 4. Nxd4 Nf6 5. Nc3 a6 6. Be3 Ng4 7. Bg5 h6 8. Bh4 g5 9. Bg3 Bg7 10. Be2 h5 11. h4 gxh4 12. Bxh4 Nc6 13. Nb3 Be6 14. Qd2 Qb6 15. Nd5 Bxd5 16. exd5 Nce5 17. c3 Ng6 18. Bf3 Rc8 19. Bg5 N6e5 20. Bxg4 hxg4 21. Rxh8+ Bxh8 22. O-O-O Kd7 23. Qc2 Rg8 24. Qf5+ Kd8 25. Be3 Qb5 26. Bd4 Qd7 27. Qh7 Rf8 28. f4 gxf3 29. gxf3 Bf6 30. Qe4 Rh8 31. f4 Qg4 32. Nc5 dxc5 33. Bxe5 Bxe5 34. Qxe5 Rh4 35. Rf1 f6 36. Qe4 Qd7 37. Qg2 Kc7 38. Qf2 Qb5 39. Re1 Rh7 40. Qg3 Kb6 41. b3 Ka7 42. Qf2 Ka8 43. Qc2 Rg7 44. Kb2 Qd7 45. Qe4 Qg4 46. Ka3 Qd7 47. Rh1 Ka7 48. Rh2 Qd6 49. Re2 Rg4 50. Qxe7 Qxe7 51. Rxe7 Rxf4 52. Rc7 Kb6 53. Rc8 Rf3 54. Kb2 Rd3 55. c4 f5 56. Kc2 Rh3 57. b4 cxb4 58. d6 Rh7 59. Kb3 Ka5 60. Rc7 Rh3+ 61. Kc2 Rh2+ 62. Kd3 Kb6 63. c5+ Kb5 64. d7 Rh1 65. Ke2 Rh2+ 66. Ke3 Rh3+ 67. Kd4 Rh1 68. Rxb7+ Kc6 69. d8=N#

To gain a waiting move

[Title "Mate in 4, T. Siers and H. Wittwer, British Chess Federation, 1935/36"]
[FEN "1R6/Pn6/K6p/7P/8/4NNp1/6P1/7k w - - 0 1"]

1. a8=N Nc5+ 2. Ka7 Nb7 3. Nc7 Nc5 4. Rb1#

To block another piece

[Title "Luke McShane-Levon Aronian, London Chess Classic, 12/4/2012"]
[FEN ""]
[startply "136"]

1.e4 e5 2.Nf3 Nc6 3.Bb5 a6 4.Ba4 Nf6 5.O-O Be7 6.d3 b5 7.Bb3 d6 8.a4 Bd7 9.c3 O-O 10.Nbd2 Na5 11.Bc2 c5 12.Re1 Re8 13.Nf1 Nc6 14.Ne3 b4 15.h3 Rb8 16.Nc4 Be6 17.Bb3 h6 18.Be3 bxc3. 19.bxc3 d5 20.exd5 Nxd5 21.Qc2 e4 22.dxe4 Nxe3 23.Rxe3 Rxb3 24.Qxb3 Na5 25.Nxa5 Bxb3 26.Nxb3 Qb6 27.Nbd2 Qb2 28.Rae1 Rd8 29.Nf1 c4 30.Ne5 Bc5 31.Rf3 Qb3 32.a5 Rd6 33.Nxf7 Rf6 34.Rxf6 gxf6 35.Nxh6+ Kf8 36.Ng4 Qxc3 37.Rd1 Qb4 38.Nxf6 Kf7 39.Nd5 Qb2 40.Nde3 c3 41.Rd5 Be7 42.Rf5+ Ke8 43.g4 c2 44.Nxc2 Qxc2 45.Ng3 Qc7 46.Nh5 Bd8 47.Kg2 Qc6 48.Re5+ Kf7 49.g5 Qa4 50.h4 Bxa5 51.Rf5+ Ke6 52.Nf4+ Kd7 53.f3 Qc2+ 54.Kh3 Qf2 55.Kg4 Be1 56.Ng6 a5 57.Rf7+ Kd8 58.e5 a4 59.e6 Bb4 60.e7+ Bxe7 61.Nxe7 Qc5 62.Kh5 a3 63.Kh6 a2 64.g6 Qc4 65.Nf5 a1=Q 66.Rf8+ Kc7 67.g7 Qc6+ 68.Kh7 Qxf3 69.g8=N Qh5+ 70.Ngh6 Qe5 71.Ng7 Qxh4 72.Rf7+ Kb6 73.Nf5 Qee4 74.Kg6 Qe6+ 75.Kg7 Qg5+ 76.Kf8 Qc8#

To avoid stalemate

[Title "Iroda Khamrakulova-Ekaterina Ubiennykh, WJun Women, Athens Greecd, 8/24/2001"]
[FEN ""]
[startply "154"]

1. e4 e5 2. Nf3 Nc6 3. d4 exd4 4. Nxd4 Nf6 5. Nxc6 bxc6 6. e5 Qe7 7. Qe2 Nd5 8. c4 Nb6 9. Nd2 Bb7 10. b3 O-O-O 11. Bb2 g5 12. O-O-O Bg7 13. h4 h6 14. g3 c5 15. Rh2 Rde8 16. f4 d6 17. Re1 Kb8 18. Bg2 Bxg2 19. Qxg2 gxf4 20. gxf4 Rhg8 21. Qe4 dxe5 22. fxe5 Qe6 23. Rhe2 Bh8 24. Nf3 Rg4 25. Qd3 Kc8 26. Re3 Bg7 27. Kb1 Rd8 28. Qc2 Bf8 29. Re4 Rg3 30. Rf4 Be7 31. Qf5 Rf8 32. Rf1 Kd7 33. Bc1 a5 34. Rd1+ Kc8 35. a4 Rh3 36. Rf1 Kd7 37. Bd2 Rb8 38. Ka2 Rg3 39. Bxa5 Rg2+ 40. Ka3 Ke8 41. Ne1 Rg3 42. R1f3 Qxf5 43. Rxf5 Bxh4 44. Rxf7 Rxf3 45. Rxf3 Bg5 46. Nd3 Be7 47. Nf4 Kd7 48. Rd3+ Kc6 49. Ng6 Bg5 50. Bd2 Rg8 51. Bxg5 Rxg6 52. Bf6 Nd7 53. Rf3 h5 54. Rf5 Rh6 55. Bg5 Re6 56. Bf4 h4 57. Rh5 Nf8 58. Bh2 Nd7 59. a5 Kb7 60. Rxh4 Ra6 61. b4 cxb4+ 62. Kxb4 Re6 63. Rh5 Ka6 64. c5 c6 65. Bf4 Re8 66. Rh6 Nxe5 67. Bxe5 Rxe5 68. Rxc6+ Kb7 69. Rb6+ Ka7 70. Kb5 Rh5 71. Rg6 Rh7 72. a6 Rf7 73. Rg5 Re7 74. Rd5 Rg7 75. c6 Rg1 76. c7 Rg8 77. Rd8 Rxd8 78. cxd8=N Kb8 79. Kb6 Ka8 80. Ne6

To get stalemated

[FEN "r4b2/4pPpP/4P1Pp/6pK/6P1/8/1k6/8 w - - 0 1"]

1. h8=N Ra1

It is simply the strongest move in the position.

[Title "Schweber-Wexler, Buenos Aires Argentina, 1964"]
[FEN " "]
[startply "90"]

1. e4 c5 2. Nf3 e6 3. d4 cxd4 4. Nxd4 a6 5. Bd3 Qc7 6. O-O Nf6 7. Qe2 d6 8. f4 Nbd7 9. Kh1 Be7 10. c4 b6 11. Nc3 Bb7 12. Bd2 O-O 13. Rae1 Rad8 14. Bb1 Rfe8 15. f5 exf5 16. Nxf5 Bf8 17. Bg5 Rc8 18. Nh6+ gxh6 19. Bxf6 Nxf6 20. Rxf6 Bg7 21. Qg4 Re5 22. Rxh6 Qe7 23. Nd5 Qg5 24. Qxg5 Rxg5 25. Ne7+ Kf8 26. Nxc8 Bxh6 27. Nxd6 Bc6 28. Rf1 Be8 29. Nf5 Bg7 30. Nxg7 Kxg7 31. Kg1 Rc5 32. Bd3 Bd7 33. Kf2 Be6 34. b4 Rc7 35. Rc1 Kf6 36. Ke3 Ke5 37. a3 f6 38. c5 b5 39. a4 bxa4 40. Bxa6 a3 41. b5 a2 42. b6 Rg7 43. b7 Rg8 44. c6 Kd6 45. c7 a1=Q 46. c8=N+ Rxc8 47. bxc8=N+
  • There is a black king missing in Suat Atalik-Anthony Miles. – user1583209 Oct 26 at 13:13
  • Not an objective reason, but still seen regularly among lower level players: underpromotion (including to a knight) is often done in cases where the opponent keeps on playing a completely lost position. Reasons could be that the player underpromting wants to practice a certain type of endgame or that he wants to send the message: hey look I will win even if I just promote to a knight only. (the latter is similar to players sometimes getting 5 queens, 100 moves and only then eventually mating the opponent). – user1583209 Oct 26 at 13:21
  • @user1583209 Thanks, and fixed. And I do tend to do that myself at times. – Rewan Demontay Oct 26 at 14:06
  • 1
    In Kucuksari-Betaneli, though 73 h8=N+ does indeed draw, any promotion does. Indeed any move except Ne7? draws. If White promotes, then 73 ... Rh1+! 74 Kg5 Rxh8! 75 Nh6+/Nf6, drawing. – Rosie F Oct 28 at 8:00
2

It can be a useful under promotion in opening traps. For instance there is a known trap line in the Albin Counter Gambit with a winning knight promotion. It's called the Lasker trap at: https://en.wikipedia.org/wiki/Albin_Countergambit

  • 1
    Ah yes. I forgot about that one. – Rewan Demontay Oct 26 at 1:05

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