PawnSac: < optimal play: 4...a6 TN >
As the database shows, a6 was played in all 5 previous games before this one.http://www.chessgames.com/perl/ches...
..a6 seems logical and necessary, as ..b4 seems weaker on several counts, such as giving up c4 to the LSB or a N (Nbd2-c4).
S Mansour vs A Fier, 2010
If black does not want to spend 3 tempi to dissolve his pawn, as in the game above, then a6 is the logical best alternative, since after ..b4 5. a3 a5 6. axb4 axb4 7. Rxa8 Bxa8 8. Nbd2 e6 9. Bd3 gives white better development and piece placement. Black hasn't proved anything, and has nothing to show for his b pawn maneuver or tempi loss.
< 13.♘c4? That only invited 13...♕c7! What's wrong with the obvious 13.♕xa4 or 13.♖xa4 >
No disagreement there! 13.Qxa4 almost forces the Q trade and lets white quickly double on the A file ..Qxa4 14.Rxa4 Nc7 15.Rfa1 Rfb8 16.Rxa8 Bxa8 17.b3 then possibly transfer the Nf3-e1-d3 and prepare the pawn advance etc. White would seem to have the winning chances in the passer.
< 16...♘b4! Puts white on the defensive >
Sure does! I don't think i would have traded with Rxa8 so quickly. The result is that black gets the A file to come down on the outside. I think i would have tried Qc1-b2 and Rfa1 to try and hold the file.