For some reason or another I had been looking at that ending a few months back, and I remembered that the "drawing zone" could be surprisingly large for the weaker side. I couldn't prove this, though, as (a) I'm not good at this kind of technical exercise, (b) I didn't actually remember anything I had (maybe) learned, and (c) Hleb outrates me by 400 points. But I kept repeating that "There's a drawing zone!" and Hleb would reply "Show me drawing zone!"
Now that I'm home and can look things up, I will show you drawing zone! Muller & Lamprecht's Fundamental Chess Endings shows a couple of examples.
Q + a5P vs Q
Q + a7P vs Q
In both cases, if Black has the move and his king is on one of the squares highlighted in green, it is a tablebase draw. But if you want the proof, you'll have to look it up elsewhere, or investigate the positions yourself!
I will add this, however: in the case of the a7 pawn, according to Muller & Lamprecht, "... h8 is a draw for specific tactical reasons, and does not constitute a drawing zone in the normal sense."
...
It seems that this ending had not merited much attention from GMs in the past. Reuben Fine in Basic Chess Endings (1941) simply states, "A RP draws just as easily as a KtP: once the Pawn gets to R7, the K to R8, perpetual check is unavoidable."
Paul Keres in Practical Chess Endings (1973, West Germany) Was slightly wordier in his exposition: "We shall not examine positions involving the RP, which only offer White slender winning chances. The reason for this is clear: White's king has difficulty escaping checks."
And of course, all of this reminded me of an anecdote from a tournament played over 40 years ago. In the 1975 Hoogovens Tournament in Wijk aan Zee, the following position was reached in the seventh round:
Jan Smejkal (2600) vs Walter Browne (2550)
After 57 ... Kc6-b5
I'll pick up with Kavalek's notes, from R.H.M.'s tournament book:
Here the game was adjourned for the second time.Walter reportedly said that he did not know how Smejkal could advance his pawn. But what seemed hard for the American was easy for the Czech. I recommend that you be patient and watch Smejkal's winning technique. It looks rather convincing, even though according to some opinions Black could have had good drawing chances.So, some practical difficulties exist!
A week after this tournament was over the Yugoslav Grandmaster Ljubomir Ljubojevic gave a clock exhibition in a small Dutch town. After five hours one game had to be adjudicated. Each player had a queen on the board and Ljubo had one pawn: it was a KRP on the fifth rank. The result was a draw but somebody pointed out that the same position was won by Smejkal against Walter Browne. The master who called Ljubo's game a draw said, "But that's impossible! How did he win it?"
Incidentally, Kavalek's book for R.H.M. on the 1975 Wijk aan Zee grandmasters tournament is my favorite tournament book of all time. Eleven of the sixteen players contributed some notes to the games, and Kavalek annotated a great many others. But Kavalek's notes before each game are what really make the book a winner, as it gives a good "slice of life" look at such a tournament. If you come across a copy somewhere, I'd recommend picking it up.
