Tuesday, September 25, 2007

Evaluate the Position


A large part of playing chess is being able to evaluate a position. Usually it is not the person who can calculate the deepest that has the advantage, it is the person who can better evaluate the positions that will arise from the calculation. In this position, from a game I recently played, the material is even, but both players have certain advantages.

Which side would you rather be, black or white? Why? What advantages and disadvantages does each side have? I will list them below, but try to think of them before looking.

White:
Advantages
1. Has the potential for controlling a partially open A or B-file.
2. Bishops on neighbor diagonals.
Disadvantages
1. Pawn Structure a little weakened (disadvantage for the end game).
2. Advanced pawns in castle position weaken king.
3. White-squared bishop and Queen blocked in.

Black:
Advantages
1. Controls open E file.
2. Unobstructed bishops on long neighbor diagonals.
3. Invasive pawn structure with no exploitable weakness.
4. Safe king position.
Disadvantages
1. White F pawn potentially may disrupt king position.

If I have missed anything or have wrongly evaluated the position please let me know. With this knowledge, we can come up with reasonable plans for White and Black.

White should seek to exchange pieces to alleviate the cramped position. He may also, if he can secure a safe king, play for counter-attack on the queen side.

Black should seek to exploit White's weakened king and try to transform his spacial and quality advantages into material advantages for a winning end-game.

It is Black's move. Do you see a tactic that will accomplish this goal?

6 comments:

The Opposition said...

quick scan: Bxg3!

TVTom said...

Black has an overwhelmingly winning position here with the two bishops sweeping into white's castle. In this position, black has an easy tactical shot with 1...Bxg3! as the Bishop cannot be captured:

1 ... Bxg3
2 h2xg3?? Qxg3+
3 Kh1 Qh2++

Therefore, the only choice black has to avoid mate is:

1 ... Bxg3
2 Kg2 Bxh2
3 Qe1! (the only move to avoid mate or if 3 Be1 Ne3+ with the royal fork of king, queen, and rook and mate to soon follow)
3 ... Bg1 (looks strongest to me)
4 KxB BxN
5 Qh4 BxB
6 Rf4 Ne3
7 BxN RxB and black is up more than the equivalent of a rook, with an easily won endgame.

TVTom said...

I of course mean above that the only choice white, not black, has to avoid mate is 3 Qe1.

Slatts said...

Yup, the opposition and tvtom are right that Bxg3 is the correct move. It cannot be taken by the pawn without mate, and Kg2 does seem to be the best move after Bxg3 (and it hardly makes the position much better for white)

I thought this was a quite "dramatic" presentation of the advantages, as tvtom said "black has an overwhelming winning position". Not all positions are quite as easy to diagnose, but this, I hope can give some ideas of things to look for.

TVTom said...

Slatts said...
"I thought this was a quite 'dramatic' presentation of the advantages, as tvtom said 'black has an overwhelming winning position'. Not all positions are quite as easy to diagnose, but this, I hope, can give some ideas of things to look for."

The power of the two bishops on adjacent diagonals sweeping the entire length of the board into the enemy castle was pretty amazing in that example. Btw, I think there are even quicker follow-throughs to make the win decisive than the one I suggested, if you play it out. Winning a pawn or two is great, but in real games, if you don't keep up the pressure, the other side can wriggle out and get counterplay. Doubling the rooks is even stronger than 3 ...Bg1:

1 ... (Bxg3)
2 Kg2 Bxh2
3 Qe1 Re5! (the N is pinned)
4 Bg5 Rce8
5 Qh4 RxB+
6 Kh3 Ne3
7 Rae1 Nxf5
8 Qg4 h5!! and the white queen is lost (it can't move away from the g3 square or ...Qg3++) and mate is forced in a few more moves.

Or if
1 ... (Bxg3)
2 (Kg2) (Bxh2)
3 (Qe1) (Re5!)
4 Kh1 Qe7 (to prevent Qh4)
5 c3 RxB
6 Qd1 Nf2+
7 RxN RxR and white cannot prevent 8 ...Qh4! followed by mate, e.g.:
8 cxd4 Qh4
9 d5 Qh3
10 Nh4 Bg3+
11 Kg1 Qh2++

jrobi said...

Excellent analysis guys - well done!