I recently had a blitz game which came to a rook + pawn vs. rook endgame. My opponent resigned in the following position:

Black can reach Lucena position here: 74. Kd1 Rc5 75. Rg8+ Kf3 76. Rf8+ Kg2 77. Rg8+ Kf1

and then it’s a known win: 78. Rg7 Rd5+ 79. Kc1 Ke2 80. Re7+ Kf3 81. Rf7+ Ke3 82. Re7+ Kf4 83. Rf7+ Rf5

By the way, Crafty found a neat and faster win – 74. … Rc8!

After I looked at all this stuff I thought that my opponent probably missed a draw earlier.  With a help of online Nalimov tablebases I found the moment where it went wrong for him:

Only rook moves – Rd2, Rd5, Rd6, Rd7, Rd8 lead to a draw. It is actually a second method of defense in Philidor position when white rook can’t get to the third line. It was found by M. Karshtedt, that you still can draw by checking from behind. White king should stay on the short side, to allow, if necessary, checks from the long side.
In my game White lost after 70. Kf2 Rc2+ 71. Ke1 Kg3 72. Rd3+ f3 73. Rd8 f2+.
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Actually the chances of playing it are lower than matching 4 out of 6 in 6/49 lottery – 1: 1,032.   I played about 4,000 blitz games, but only yesterday for the first time ever I got Philidor position  ( I never got it in OTB, online correspondence, standard FICS, etc. games).

56. … Kf7  The Black King is going to the queening square of the pawn. The rook is already on the sixth rank, not allowing the White King to advance. 

philidor1

57. Ra7+ Kg8 58. Kf5 Rb6 59. Re7 Rc6 60. g6 – this is what Black is waiting for,  now there is no defense from the checks from behind

philidor2

60. … Rc1 61. g7 Rf1+ 62. Kg6 Rg1+ 63. Kf6 Rf1+  

philidor3

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