Friday, April 27, 2012

(Not) Winning a Won Game

Here's another game from last month's ICA Girls' Invitational Championship at the North Shore Chess Center.  I hope that both Adele and Miranda will forgive me for publishing a game in which they made 51 good moves and only one bad one.  But I found this game so instructive because it's so typical.

The stylish way to win a game is by direct attack against the enemy king.  In real life, we don't get to be stylish as often as we'd like.  So we win a piece instead.  When we talk about "winning a piece" in chess, we mean winning a bishop or a knight, worth about three pawns.  In this game,  Miranda wins a piece for a pawn: in quiet middlegame positions, this advantage is usually sufficient for a win.

When you win a piece for a pawn, what's the easiest way to win?  Well, you'd like to use your extra material to queen a pawn and then checkmate with overwhelming force.

But put yourself in your worthy opponent's shoes.  You may be winning, but you have one less pawn than she does.  So if the defender could keep trading one of her pawns for one of your pawns until there was only one pawn left, that extra pawn would be hers.  True, you would still be up a piece, but you'd have to look for a way to checkmate without making a queen.  That's much harder!  (Rule of thumb: in pawnless endings, one often has to be up by five "points" to win.) 

DEFENDERS WANT TO TRADE PAWNS, NOT PIECES.  (Here, we use "pieces" in a second sense: kings, queens, rooks, bishops, and knights, but not pawns.  Yes, I know we can't trade kings.  And yes, we usually talk about chess sets having thirty-two pieces, not sixteen pieces and sixteen pawns: this third meaning of "piece" is actually the most common one.)

THE SUPERIOR SIDE WANTS TO TRADE PIECES, NOT PAWNS.  Every pawn is a potential queen.  Guard your potential queens just as you do the one that's already on the board!

Adele Padgett – Miranda Liu [D45]
ICA Girls’ Invitational
March 31, 2012

1.d4 d5 2.c4 e6 3.Nc3 Nf6 4.Nf3 Be7 5.e3 0–0 6.Be2 c6 7.0–0 Nbd7 8.Bd2 dxc4 9.Bxc4 b5

White to play
Miranda chooses a Meran Variation setup. As White's bishop is not that active on d2, Black should get nice play.

10.Bd3 Bb7 11.e4 a6 12.Rc1 c5 

White to play
 The typical Meran break.


Positionally, this is a good move, but there's a tactical refutation.

13...cxd4! 14.Nxd4

14.Ne2 saves a piece, but looks ugly.

Black to play

Black wins a piece by force, as White's configuration of pieces on the d-file isn't stable.

15.Be3 Nxd3 16.Qxd3 e5

Horsie is pinned.

17.Red1 exd4 18.Bxd4 Rc8 19.a3 Bc5 20.Bxc5 Qxd3 21.Rxd3 Rxc5

Good technique so far: Black wants to trade pieces

White to play

White has only one pawn for the piece. In a quiet position like this one, it's hard to put up resistance unless one has two pawns for the piece. The best strategy is to sit tight, have the pieces and pawns protect each other, and hope for a Black mistake.

22...h6 23.Rcd1 Rfc8 24.Kf2 Kh7

The move in the game is objectively fine, but I would prefer 24...Kf8 bringing the king closer to the center.

25.R1d2 Re8 26.Rd4 Rc7 27.Rd6 Ree7 28.Ke3!

White has nothing else going for her, so she might as well centralize her king.

Black to play

Exchanges of pieces help the superior side: swapping rooks is good for Black.

29.Rxd7 Rxd7 30.Rxd7

30.Rc2 might offer slightly better resistance: the defender wants to exchange pawns and keep pieces on the board.

30...Nxd7 31.Nd5 Kg6

31...Bxd5! 32.exd5 Kg6 should be an easy win.

32.Ne7+ Kf6 33.Nf5 h5 34.Nd6 Bc6 35.Ne8+ Kg6 36.Nc7 a5 37.Nd5 Bxd5! 38.exd5

Now Black needs a plan. One idea is to stop the d5 pawn with the king, and win the pawn with the knight.


38...Kf6! 39.Kd4 Ke7 40.g3 Kd6 41.h3 Nb6

39.Kd4 g5 40.g3 

Black to play: are you a human or a computer?

The computer actually likes this move for concrete reasons (it calculates a forced win). But on general principles, why should Black exchange pawns? This helps the defender!

41.axb4 axb4 42.b3 g4 43.f4 f6 44.Kc4 Ke4 45.d6 

Black to play: look for a simple win

I'm sure you all saw that Black wins by one tempo after 45...Kf3 46.Kxb4 Kg2 47.Kb5 Kxh2 48.Kc6 Nf8 49.b4 h4 50.b5 hxg3 51.b6 g2 52.b7 g1Q 53.b8Q Qh1+ 54.Kc7 Qc1+ 55.Kd8 g3 Black is right to avoid messy complications: why give White any counterplay?

46.Kxb4 Kd5!

46...Kf3? doesn't win any more: 47.Kb5 Kg2 48.Kc6 Nf6 49.b4! Kxh2 50.b5 h4 51.b6 hxg3 52.b7 g2 53.b8Q g1Q 54.Qh8+. Don’t bother calculating variations like these unless you have to: look for the easy way to win!

47.Kc3 Kxd6 48.Kd4 Nb6 49.b4 Nd7

White really can't improve the position of her pieces.


Black to play: eliminate counterplay!

50...Kc6 51.Kd4 Kb5?? 52.Kd5!


Black to play:
It is easier to sacrifice a piece when one has an extra piece

51...Nd5 forces White to move a piece to a worse square. 52.b5 (52.Kc4 Nxf4! (a key idea!) 53.gxf4 h4 54.Kd3 g3 55.hxg3 h3) 52...Nb6 53.Kd3 Kc5 (yummy pawn on menu) 54.Ke3 Nd5+ (no hurry) 55.Kd3 Nf6 (no hurry) 56.Ke3 Ne4 (you get the idea) and Black will enjoy lunch only when her pieces are placed optimally.

52.Kc4 Nb6+??

This move allows 53.Kd4 with triple occurrence of position. (Petrosian once made the same mistake against Fischer.)  Like golf, chess is frustrating and humbling: one slip can spoil a good round!


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