# How can a human figure out best move in this position?

Why is 12. b4 played by a GM? Why doesn't he just capture the bishop? And how can he forsee so far in the future? Am I missing something?

• Looks like a great game. Can you tell us who the players are and what is the venue ? Aug 17, 2018 at 7:03

Maybe before justifying the pawn sacs one should answer more convincingly why taking on c3 would not have pleased White. The answer is the backward pawn on c-file and future pressure against it by rooks from c-file. Black cannot be happier if the Queens get exchanged on c3 as well. So, taking the bishop back on c3 would have yielded nothing for White. b4 is half out of desperation as it is of creativity!

Augment to this the forcing sequence delineated by the other answers here, and you see that b4 is not as much of an abnormal move as it may look initially.

• Since 12.bxc3 is unpleasant for White, it seems that White must have already been planning the attack with 12.b4 when he played 11.a3. Otherwise White might have played 11.Rc1 to avoid the backward pawn. So maybe it was preparation rather than desperation.
– bof
Aug 15, 2018 at 22:34
• 12 Qxc3 Qxc3 13 bxc3 seems roughly equal -- White will soon play c4 before Black can start piling up on the c-file or blockading c4, and White also has the two bishops FWIW. Still 12 b4 looks much better. Aug 16, 2018 at 0:52
• With desperation I meant if white is to justify their opening. Aug 18, 2018 at 20:21

This position is close enough to the beginning of the game that the grandmaster may have already analyzed it at home.

Even at the board it is reasonable to analyze the forcing sequence 12 b4 Bxb4 13 axb4 Qxb4 14 Rfb1 Qe7 (Qd6? 15 Bg3) 15 Qc6 Rb8 16 Rxa7. Now we can pause to evaluate. White has recovered one of the sacrificed pawns and has a very active position, while Black hardly has a reasonable move: both Knights are pinned to the Queen, and any move by Rb8 or Bc8 drops material. White threatens 17 Bg3, attacking the trapped rook, which Black can't free with b5 because after 17 Bg3 Rb6? White can play 18 Qxb6 anyway. If 16 . . . Ne5 White at least has 17 dxe5 Qxa7 18 exf6 winning two pieces for the Rook.

(I'm analyzing this from the diagram, and may well have missed something. But I'm no grandmaster, and never got as high as 2300 USCF before I played tournament chess 25+ years ago. So for an actual grandmaster this kind of analysis should be routine once the GM had made the leap of imagination to consider 12 b4!)

• +1. The answer to "And how can he forsee so far in the future?" is : "That's really not that far! Aug 17, 2018 at 7:01

If you take the bishop by pawn or queen -- you'll get an equal position with approximately even chances.

After `b4`, and exchanging pawns for a bishop, there's a good attack on queen side, with `Rfb1`, then black queen has to find the safe place, and `Qc6` with quite good chances to win a piece.

It's actually a very nice idea. The point is that after:

12.b4 Bxb4 13.axb4 Qxb4 14.Qc6!, White is getting plenty of queenside activity, and is going to win the a7-pawn since Black's rook will have to move to b8. White will still be down a pawn, but will have tremendous queenside activity.

So the point of 12.b4 is that it allows White's queen access to the c6-square, while still winning Black's bishop.

Note that after 12.b4, Black must play 12...Bxb4, or else he just loses his queen since it's trapped.

As for how the GM could have foreseen this, it takes a combination of natural talent and countless hours of practicing calculation to ingrain patterns into the mind. Although I wouldn't say this combination is close to GM calibre, maybe 2200 level at best.

I assume the last move was b2-b4. The idea is 1...Bxb4 2.Rfb1 threatening to trap the queen with axb4. So Bishop somewhere (2...Be7). Now can we trap that queen or something? 3.Rb5 queen a6 is only open square which allows Rook discovery...but I don't see a win here. hmmm, 4.Rc5 Qb7 (4...b5!?) 5.Rc7 Qb8 6.Bg3!?

Okay this line is total junk as pointed out in comments and the answer is far simpler. Black has problems with the unprotected Rook on a8 and it can't find a home on b8 because Bg3.

• Stockfish evaluates the position as +3 after 1. .. Bxb4, but -2.7 after 2. Rfb1. After 2 .. Be7 3. Rb5 Qa6 4. Rc5 Qxd3 5. Qxd3 bxc5, white is down to -4.5. Aug 15, 2018 at 16:31
• @Dennis Nice, I guess I am rusty, so what did the GM see 2.Qc6 maybe. Aug 15, 2018 at 16:39
• Still according to Stockfish, the best continuation is 2. axb4 Qxb4 3. Rfb1 Qe7 4. Qc6, as suggested by lenik. Aug 15, 2018 at 16:43