# Why does Black play 10...a6 in the A39 variation of the English opening?

I observed that after

``````[fen ""]

1.c4 c5 2.Nf3 Nc6 3.d4 cxd4 4.Nxd4 Nf6 5.Nc3 g6 6.g3 Bg7 7.Bg2 O-O 8.O-O Nxd4 9.Qxd4 d6 10.Qd3
``````

In many games, Black played the strange move `10...a6!?` It has been played by top players like Kasparov, Anand and Carlsen.

What is the point of `10...a6?` Is it a waiting move for White to reveal his hand? It seems like a preparation for a future `b5`, but why at this particular moment when Black could simply develop the bishop on `f5 (10...Bf5)`? Also, in some variations, the pawn could be useful on `a5` so that Black's knight can rest comfortably on `c5`, so `10...a6` could be a waste of a move.

• Here is the link to the question describing how to create chess diagrams. I think that my answer and response made to the member RauanSagit's comment will be helpful to you. Best regards. Commented Feb 9, 2014 at 3:40
• Perhaps Black targets `Qc7` + `Be6` + `Rc8` lineup to pressure `c4` pawn and wishes to protect himself from `Nb5` jump. Also, in some cases Black can play `b5` to open lines which should give him compensation for the sacrificed pawn in view of active piece play. Just a thought... Best regards. Commented Feb 9, 2014 at 7:48

This position is discussed in many books, the consensus being that `10... a6` is the best and most flexible move. As you say, black waits for white to reveal their hand, and `a6` is generally useful. Play could continue `10... a6 11. Be3 Bf5` or `10... a6 11. Bd2 Rb8`.

The move `10... Bf5` is a serious alternative since it provokes `11. e4`, blocking the diagonal for white's bishop. In this variation white would ideally like to hold back `e4` to keep the diagonal open. Still, white can keep an advantage in various ways. Marin in Grandmaster Repertoire 5 says that white should try to emulate Smyslov-Timman, Moscow 1981.

White often chooses a set-up with `Bd2`, `b3` and `Rac1`, leaving black's `Bg7` bishop with nothing to attack. In such a position black needs the `b5` break to create active play. Therefore playing `a5` is usually not a good idea.

The starting position is the following (including the two options 10...a6 and 10...Bf5)

``````[FEN ""]
1. c4 c5 2. Nf3 Nc6 3. d4 cxd4 4. Nxd4 Nf6 5. Nc3 g6 6. g3 Bg7 7. Bg2 O-O 8. O-O Nxd4 9. Qxd4 d6 10. Qd3 a6 (10...Bf5).
``````

Why did white choose Qd1-d3? First of all, this prepares to increase the control over the d-file with Rf1-d1 or Ra1-d1. Second of all, this protects the c4-pawn against Bc8-e6. Next, white is planning Rf1-d1 and c4-c5 to attack the d6-pawn. If black places the Queen on c7, then white has Bc1-g5xf6 followed by Nc3-d5xf6, ruining the enemy pawn structure.

Black's Bc8 has to guard the b7-pawn. Another piece has to take over this role, if the Bc8 wants to move to a better square. Black could try Qd8-b6 to protect the b7-pawn and put pressure on the enemy b2-pawn. Yet, 10...Qb6 is met by 11.Nb5 followed by 12.Be3. Black also has the thematic Nf6-d7-c5 or -e5. The problem is that white might have time with Nc3-d5 and Bc1-g5, which would cause trouble for the e7-d6 pawn chain. Black can also try Qd8-a5-h5, planning a kingside attack with Bc8-h3. Yet, 10...Qa5 is also met with 11.Nb5. Thus, 10...a6 prepares 11...Qa5 or 11...Qb6.