CHESS: The Rules for Drawing

If the last 50 consecutive moves have been made by each player without the movement of any pawn and without the capture of any piece, the game can be declared a draw by either of the opponents. The other player's approval is not required, and the game ends immediately and is recorded as a draw for both players.

I was under the misapprehension that a draw could be claimed if 50 consecutive moves had been played without the capture of a piece. I'd forgotten or never knew about the requirement for no pawn moves to have occurred either. I had reason to recall the rule because I ended up playing a 3-D game on OS X that I eventually lost and in which Black carefully avoided a draw. It was an instructive game and it was surprising that I could hold out for as long as I did. Here are the moves:

1. d4 d5 2. Nf3 Nf6 3. e3 c5 4. c3 cxd4 5. cxd4 e6 6. Nc3 Bd6 7. Bd3 O‑O 8. O‑O Nc6 9. a3 Bd7 10. Bd2 Qb8 11. h3 a6 12. Rc1 Rc8 13. Qe2 Qa7 14. Na2 Rc7 15. b4 Rac8 16. Rc2 Ne4 17. Rfc1 b5 18. Be1 e5 19. dxe5 Nxe5 20. Nxe5 Bxe5 21. Rxc7 Rxc7 22. Rxc7 Qxc7 23. f3 Bh2+ 24. Kf1 Ng3+ 25. Bxg3 Bxg3 26. Qc2 Qxc2 27. Bxc2 Be5 28. e4 dxe4 29. Bxe4 Be6 30. Nc1 Bc4+ 31. Kf2 Bd4+ 32. Kg3 Bb2 33. Nd3 Bxd3 34. Bxd3 Bxa3 35. Be4 Bxb4 36. Bc6 Bd6+ 37. Kf2 b4 38. Ke2 b3 39. Kd2 Bb4+ 40. Kc1 Bc3 41. Bb7 a5 42. Bc6 Kf8 43. Ba4 b2+ 44. Kb1 f5 45. Bc2 Bd4 46. Ka2 g6 47. Kb3 Ke7 48. Kc4 Be5 49. Bb1 Ke6 50. Kc5 h5 51. Kc4 h4 52. Kd3 a4 53. Ke3 g5 54. Kd3 a3 55. Ke3 Bd6 56. Kd4 Kf6 57. Ke3 Ke5 58. Ba2 Bc5+ 59. Kd3 Kf4 60. Ke2 Kg3 61. Kf1 Bd4 62. Bb1 Kf4 63. Ke2 Bb6 64. Ba2 Bg1 65. Bb1 Bb6 66. Ba2 Bd4 67. Bb1 Kg3 68. Kf1 Be3 69. Ba2 Bd2 70. Bb1 Kf4 71. Ke2 Bb4 72. Ba2 Bd6 73. Bb1 Kg3 74. Kf1 Kf4 75. Ke2 Kg3 76. Kf1 Bc5 77. Ba2 Bb6 78. Bb1 Bd4 79. Ba2 Kf4 80. Ke2 Bb6 81. Bb1 Kg3 82. Kf1 Kh2 83. Ba2 Bd4 84. Bb1 Bc3 85. Ba2 Kg3 86. Bb1 Be5 87. Ba2 Bc3 88. Bb1 Be5 89. Ba2 Kf4 90. Ke2 Bc7 91. Bb1 Kg3 92. Kf1 Bb6 93. Ba2 Bf2 94. Bb1 Bd4 95. Ba2 Bc5 96. Bb1 Bb6 97. Ba2 Ba5 98. Bb1 Bc3 99. Ba2 Bd2 100. Bb1 Kf4 101. Ke2 Bb4 102. Ba2 Kg3 103. Kf1 Bc5 104. Bb1 f4 105. Ba2 Bb6 106. Bb1 Bc5 107. Ba2 Be3 108. Bb1 Bf2 109. Ba2 Be3 110. Bb1 Bf2 111. Ba2 Bb6 112. Bb1 Kh2 113. Ba2 Bd4 114. Bb1 Kg3 115. Ba2 g4 116. hxg4 h3 117. gxh3 Kxf3 118. g5 Ke3 119. h4 Kd2 120. h5 Kc2 121. g6 Bg7 122. Kf2 b1=Q 

I'll show the position I reached before it all went wrong for me. Black has just played 25...Bxg3 and I mistakenly decided to exchange Queens, after which the White pawn on a3 cannot be defended.

White has just played 34.Bxd3 and Black is now ready to play 34...Bxa3 and there's nothing White can do about it. Things look grim for White.

It would seem that two connected Black pawns on the queenside would be unstoppable if the White King is not present but such is not the case because the White Bishop is quite up to the task of holding off the Black pawns all by itself. However, White must keep the Black King from penetrating to the queenside. Because White can move the Bishop from b1 to a2 and back again, the White King cannot be forced to yield ground to the Black King. On move 53, Black played 53...a3 and Black did not move another pawn until 50 moves later:

Now Black on move 104 is well aware that another King or Bishop move would result in a draw because 50 moves would have passed since the last capture or pawn move. To avoid this, Black plays 104...f4, moving the pawn on f5 to f4.

After Black's 115th move, 115...g4, things fell apart quickly for White. I don't think there are viable drawing options for White but I'm not completely sure.