Sunday, June 29, 2014

Nontrivial

I think I have lost respect for pawn endings. Arrogance requires that you look down on something, so why not the pawn? But I had to eat humble pie when going over a few pawn endings recently. Two are from Chernev's Practical Chess Endings, mentioned earlier in my post Winter Melon. The third is from my own game where I probably prematurely agreed to a draw.

Practical Chess Endings #26
Grigoriev 1932

White to play and win

White has the distant rook pawn. Black has a bishop pawn. With White to move, Black can stay in the square of the pawn, so it's likely a king move is in order. The shouldering type of move to knock Black off the h1-a8 diagonal begins with 1.Kf5! Ke3 2.Ke5! If Black persists all the way to 2...Kd3 3.Kd5 Kc3 4.Kc5, Black can't approach the pawn with 4...Kb3, but 4...Kb2 5.a4 easily loses. Instead, Black tries to disrupt the path of White's king. 2...c6 3.a4! White's pawn escapes from being chased down by Black's king. In order to ensure his pawn is not captured with 3...c5 4.Kd5, Black has to move 3...Kd3 4.a5! c5 5.a6! c4 6.a7! c3 7.a8Q! c2. White must be careful because of the drawing chances afforded by the bishop pawn. If Black's king can get to a1/b1, it's a draw because Black either queens or gets stalemated by Qxc2. Luckily, the White king is close enough to play a part. 8.Qd5+! and depending on where Black moves, White needs to continue to use precise moves.

Variation 1A: 8...Kc3 9.Qd4+! Kb3 10.Qa1! I like how White's queen beats the Black king to the corner. After Qc1, White can patiently move up his king and capture the would-be Black queen.

Variation 1B: 8...Ke3 White must notice that on e3, the Black King is skewerable to a possible new Black Queen on c1. 9.Qg2! is the only move that wins. Other moves allow Kd2 and draw ensues. If Black queens with 9...c1Q, then 10.Qg5+! skewers. The only other move available to Black is 8...Kd3. Here, the same 9.Qg5! ensures Qc1 blockading the pawn if necessary.

Variation 1C: 8...Ke2 White must delay the pawn and get his king closer for mate. 9.Qa2! is another only winning move. 9...Kd1 10.Ke4 c1Q 11.Kd3! and Black is helpless.

Practical Chess Endings #26
Grigoriev 1931

White to play and win

White is actually behind in material. If Black were to move, he could distract White's king starting with 1...g5 just long enough for the Black king to at least reach f8 to pin White king on the h-file. One key idea is that in a queening race, White needs to queen at g8 with check in order to win. This explains the funny roundabout paths that the White king takes in forcing Black to sacrifice the g-pawn.1.h4! h5 2.Kf8! g6 3.Ke7! g5 4.hxg5! h4 5.g6! h3 6.g7! h2 7.g8Q+!

Tournament Game

White to move, Black to press for a win

Note that this board is flipped so that it's from Black's point of view. This last position is the second-to-last position of a game that I played just three weeks ago. White had the move and offered a draw. I, playing Black, said to my opponent that he should properly make a move and then offer his draw. With best play, the position is a draw, but there's more than meets the eye. Here are a few scenarios to show it.

In the actual game, White played 1.a5 and offered the draw. Black to play for a win should keep pawns on the board with 1...b5 Then White has to decide what to do with his move.

Variation 3A: 2.g4 fxg4 3.Kxg4 Kd5 4.Kf5 Kc4 5.Ke5 Kxb4 and White has no hope of stopping a pawn from queening.

Variation 3B: 2.Kg5 Ke5 3.Kg6 f4! 4.gxf4+ Kxf4 5.Kf6 Ke4 White captures Black's pawns and queens without difficulty.

Variation 3C: If White tries to wait it out, Black can force things. 1.Kf3 Kd5 (1.Ke3 Ke5 2.Kf3 Kd5 transposes; 2.Kd3 Kd5 just puts White further behind the race with either 3.Kc3 Ke4 or 3.Ke3 Kc4) 2.Kf4 Kc4 3.Kxf5 Kxb4 4.g4 Ka4 (4...Kxa5 loses because the b-pawn gets slowed down by a chasing White King acting as the Winter Melon.) 5.g5 b4 6.g6 b3 7.g7 b2 8.g8Q b1Q+ and Black can try to push for the win with one extra pawn. It's a tablebase draw, but Black risks little if he wants to pursue it.

The same variations tend to happen even if White leaves the queenside pawns alone. The Black King is closer to capturing the queenside pawns and can use a timely b5 to get them even closer.

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