Once I encountered an opponent who used a very early a6 in his Sicilian Opening.
[FEN ""] 1. e4 c5 2. Nf3 a6
What could have been his objective with this move and how should I have have countered it?
This is called the O'Kelly variation of the Sicilian.
If white plays normally (i.e.
White's best plan is to play either
An unambitious plan for white would be to play into a closed Sicilian - in the closed Sicilian, black frequently plays a6-b5 in order to get counterplay on the queenside. Furthermore, in the closed Sicilian, tempi matter a lot less because the position will not change radically from one move to the next.
As I understand it, the purpose of
It seems premature, because white might not want to go there anyway (for some time). Meaning that it could easily become a wasted move.
As White, I would concentrate on king side development, knowing that b5 was "off limits," but not caring, because I have "better" things to do.
One disadvantage of a6 is that Black may want to play a5 later to try to "chase" a White knight on b3. But if he does so, he would have wasted a move with a6.
The point of ...a6 is to control the square b5 where white can otherwise place a knight or bishop at some point. Another point is to prepare b7-b5 followed by Bc8-b7 and perhaps b5-b4 to chase a white Nc3. The move ...a6 appears in at least two variations, 1.e4 c5 2.Nf3 d6 3.d4 cxd4 4.Nxd4 Nf6 5.Nc3 a6; 1.e4 c5 2.Nf3 e6 3.d4 cxd4 4.Nxd4 a6. If you have ever been interested in the gambit 1.e4 c5 2.b4, then you can consider 1.e4 c5 2.Nf3 a6 3.b4.