ErictheRed wrote on 02/16/11 at 17:45:02:

To me your post was completely clear. In the normal Benkö (ie with Bxa6) the whole idea of ...Ra7 is to follow up with ...Qa8 and ...Rb8. This has been known since a game Gheorgiu-Beljavsky some 30 years ago.
Instead of that last move Rb8 and because of 13.a4 I would be very tempted to play for ...c4 idea landing an octopus on d3, in which case the rook might be better on c8.

ErictheRed wrote on 02/16/11 at 07:32:41:


It may not be clear if the black rook is better on a7 or a8, but my argument is about lines with White playing a4. After the mainline (without 6.a7) you mention the "legitimate" 12.h3, but comparing it to the line with 6.a7 is not useful, since White does not play a4 in these lines.

The theoretically more relevant question is if 12.a4 in the mainline is better than 12.h3. The trend in recent correspondence chess is, that White has a big statistical edge after 12.a4. And since these were games played after 2005, these should be decent games with heavy computer use and while corrchess players have not Khalifmanns positional insight, the overall quality of the games should be very good and tell something about who has problems in that line.

In the Variation with a7 and 13.a4, two correspondence games were played which do not make me like Blacks chances: 


13...Db6 14.Te1 Tfa8 15.Sb5 Tb7 16.Sd2 Se8 17.Sc4 Da6 18.Ld2 Sb6 19.Sa5 Td7 20.Db3 h6 21.Sc6 1-0  Loinjak,S (2518)-Leonard,M (2198) 2009 - I doubt if the game really was over in that final position, but Black was already clearly worse.

13....Sb6 14.Te1 Da8 15.Dc2 Sfd7 16.Lg5 Se5 17.Sxe5 Lxe5 18.Lh6 Tc8 19.b3 Tb7 20.Tab1 Tbb8 21.Tec1 Db7 22.Sb5 Ta8 23.Sa3 f5 24.f3 Dd7 25.De2 fxe4 26.Dxe4 Df5 27.Le3 Df7 28.Lxc5 Sxd5 29.Ld4 Lxd4 30.Dxd4 Txc1 31.Txc1 Tf8 32.De4 Sf6 33.Dc4 Sd5 34.De2 Df6 35.Sc4 Tb8 36.Dd2 Df7 37.Dd3 Df5 38.Dxf5 1–0 Dutra,A (2507)-Riemer,W (2323) Corr 2009

And if I can choose between an offbeat line like 6.a7 oder a mainline, both almost by force leading to a very similar position, I would choose the offbeat line. Especially since some games show that b5 is at least a temporarily interesting place for White´ knight and Blacks choices are fewer. E.g. 12.a4 Qa5 in the mainline is Black´s second most played option (behind Qb6) and this is dubious in the a7 - line: 12.a4 Qa5?! 14.Nb5 Rb7 15.Bd2

Reading through the newly revived thread on White´s best weapon against the Benkö, I revisited my idea mentioned above. It seems common sense, that 5....Ba6 6.b3 is good for white, leading to the remaining question

What´s the use of 5....g6 6.a7 Rxa7, placing the black rook on a7 instead of a8?

A pretty forcing line in the King´s walk system often used by Karpov goes 6.Sc3 Lxa6 7.e4 Lxf1 8.Kxf1 d6 9.g3 Lg7 10.Kg2 0–0 11.Sf3 Sbd7 and now White usually played 12.h3 or 12.Re1

The latest trend in correspondence chess seems to be 12.a4, scoring 72% in 34 games, which is not a sufficient bases for conclusions if it all were mistake-prone otb-games, but in 24 corrchess games from 2006-2010 (meaning: quality chess engines were used) White scores 77%. Regarding that there is no logical way to avoid the position after 12.a4, this should make Benkö-players nervous.

Coming back to 6.a7: Now 6...Txa7 7.Sc3 La6 8.e4 Lxf1 9.Kxf1 d6 10.g3 Lg7 11.Kg2 0–0 12.Sf3 Sbd7 13.a4 reaches the same position (except for the rook placed on a7 than a8) than the above mentioned line in the same forcing way. Here the rook on a7 seems to make play even more awkward for black, since White can play Sb5 in some lines attacking the rook and winning a tempo.

Shouldn´t that give Benkö fans some sleepless nights?

to my mind 4.Qc2 is a sound side-line. White wants to play e2-e4, but waits with the development with the N on b1 till Black decides what to do with his b5-Pawn. Critical variatin starts with 4...bxc4 5.e4 If i remember correctly there was survey on it by GM Igor Stohl in CBM 130 and in the new Yearbook 92 there is supposed to be a Survey by GM Moskalenko on it (title: how to refute the Benko or like that). Both are from the whites perspective

4.a4 is worth a try

C. Ward - T Werbeck, Gent Op 2004
1. d4 Nf6 2. c4 c5 3. d5 b5 4. a4 bxc4 5. Nc3 d6 6. e4 g6 7. Bxc4 Bg7 8. f4 O-O 9. Nf3 Ba6 10. Bb5 Qb6 11. Nd2 Ne8 12. Nc4 Qd8 13. O-O d4+ 14. Be3 Bxe3+ 15. Nxe3 Nc7 16. Qe2 Bb7 17. Bc4 Nd7 18. a5 a6 19. Ng4 e6 20. Nh6+ Kg7 21. Nxf7 Qe7 22. Nxd6 Qxd6 23. e5 Qe7 24. d6 Qh4 25. g3 Qh3 26. dxc7 1-0

Larry Evans once had an apt comment about 4. b3 -- that it in effect lets Black get away with murder.  (It also lets him weaken White's pawn chain by moving the base of it up the board, one might say.)

I think some books have cited Masera-Benko, which shows the sort of "accident" White would have to try to avoid.

TN wrote on 09/07/09 at 09:56:31:


I don't see the logic of 3...cd after 3 e3  letting white get a mainstream opening like a Panov, isn't 3...g6  more logical especially for a Benoni/Benkoplayer aiming on getting an unthreatening line of Benoni or Grunfeld?