First, 13.a3? is a serious lemon (b3 or cxd5 look required). But it seems so natural! White's position seems so solid! But Najdorf spots the weakness and forces Tartakower to give up castling or lose the c4 pawn.

17.Bg3 is a nice idea, pinning the pawn to the Queen, and Black has an even nicer idea for getting out of it.

The biggest inaccuracy is 69.Rf6? instead of 69.Rf4+ (which results in mate in 31). Strange move, Rf6, when Rf4+ looks so obvious.

There is a good analysis of this ending in “Chess Fundamentals” by José Capablanca, (Algebraic edition revised by Nick de Firmian), Random House, Inc. ©2006, at pages 54-56.

The more important single thing to know is how to handle the position below as White on move. It involves an interesting use of triangulation (more commonly encountered in pawn endings):

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Here is Capablanca’s explanation: “Above is one of the standard positions that Black can often bring about. It is now White’s turn to move. If it were Black’s turn matters would be simple as the rook would have to move away from the king <[Comment: If, with Black to move in the above position, 1. …♔c8, then 2. ♕a6 pins the rook and wins it next move. -- Peligroso Patzer]>, when it would be comparatively easy to win. We deduce from the above that the main object is to force the black rook away from the defending king, and that in order to compel black to do so we must bring about the position in the diagram with BLACK to move. Once we know what is required, the way to proceed becomes easier to find. Thus:

“1. ♕e5+ (Not 1. ♕a6 because [1. …] ♖c7+ 2. ♔b6 ♖c6+ 3. ♔xc6 stalemate. (The beginner will invariably fall into this trap.)

“1. … ♔a8 (or a7) 2. ♕a1+ ♔b8 3. ♕a5

“In a few moves we have accomplished our object. The first part is concluded. Now we come to the second part. The rook can only go to a white square, otherwise the first check with the white Queen will win it. Therefore

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“The student is left to find this out by himself. The points to bear in mind are that the rook must be prevented from interposing at b8 because of an immediate mate, and in the same way the king must be prevented from going to either a6 or c8.

“There are positions of queen vs. rook where the winning procedure is very difficult, but then the most stubborn defense is even more difficult to find. Note that in this ending the key to the winning maneuvers is often the checks at long range along the diagonals. Also, the king and queen are usually kept on different lines. The student should carefully go over these positions and consider the possibilities not given in the text.”

Much better is the real <Chess Fundamentals> and not de Firmian's "butchery" (as Edward Winter calls it http://www.chesshistory.com/winter/...).>

Btw, that's what Capablanca had to say about it:

<He has done nothing of the kind, and Capablanca would obviously be devastated. In the 1934 Preface to the US version he wrote:

‘... Chess Fundamentals is as good now as it was 13 years ago. It will be as good a hundred years from now; as long in fact as the laws and rules of the game remain what they are at present. The reader may therefore go over the contents of the book with the assurance that there is in it everything he needs, and that there is nothing to be added and nothing to be changed. Chess Fundamentals was the one standard work of its kind 13 years ago and the author firmly believes that it is the one standard work of its kind now.’> http://www.chesshistory.com/winter/...

I like 20...e4. The pawn cant be attacked and sits there like a bone in white's throat for the next 8 moves. White finally deals with the pawn on move 28. By then Black has built up an attack while white's play is restricted.

What other move were you looking at for blacks 20th?

Yes, but only because nobody bothers to play these out if all the pawns are gone: they're too easy. QvR, in contrast, is difficult and highly uncertain in practice: I've seen a crucial last-round championship game hinge on QvR, with the Rook holding a draw.

The final position is a win in 20 moves. For any one who wants to see an example of accurate play in this ending, here is one line with best play for both sides (most moves holding out until mate for White's moves; fewest moves to force mate for Black - Note: in many instances through the course of the line given below, there are multiple moves that are "equal best"): 74.♔g7 ♕d6 75.♖f6 ♕d7+ 76.♖f7 ♕d8 77.♖f1 ♕d4+ 78.♔h6 ♕e3+ 79.♔g7 ♔g5 80.♔f7 ♕d3 81.♖g1+ ♔f5 82.♖g7 ♕d8 83.♖h7 ♕d5+ 84.♔g7 ♔g5 85.♖h2 ♕e5+ 86.♔f7 ♕xh2 87.♔e6 ♕d2 88.♔e5 ♕d3 89.♔e6 ♕d4 90.♔e7 ♕d5 91.♔f8 ♕d7 92.♔g8 ♔g6 93.♔f8 ♕d8#.