Saturday, September 08, 2007

A swindle and another BOOC ending

I had some interesting positions from the coffeehouse this week.

Here is one from a game I was losing. It was a complicated middle game where we both had chances. My opponent sacked the exchange and got a couple pawns for it. We pick up a position where I'm barely hanging on, trying to harrass my opponents two minor pieces to keep him from making progress. Then I spot a swindle:

Black to move

After Rg7+, black blunders with Kh4?. Checkmate follows in two moves.

I also wound up in another bishops of opposite color endgame. I believe this is not just a simple draw because of the presence of the rooks. Here is one interesting point.

Black to move

There must be something I am mis-remembering about this position since Ra8 just hangs the rook to Bxa8 -- For now I imagine the rook might have been on b6.

The white king is approaching black's passed pawns. Black wants to keep the king away and at the same time try to penetrate and attack white's kingside pawns. Unfortunately, the rook is tied down to the defense of the b-pawn. Since b4 allows Kc4, black has to find Ra8! where the response Rxb5 is met by Ra3+ Ke2 (Ke4 Re3#) Ra2+ Kf1 Rf2+ followed by taking the bishop or a discovered check to win the rook.

We pick up the game a little later. Black was able to bring the rook around and win the a2 pawn. Now black threatens the b3 pawn. White has found a way to defend it twice.

Black to move

Here I chose a simplifying sacrifice. Bxg3+ Rxg3 Rxg3 Kxg3 b3 and white doesn't have the resources to stop so many pawns. Notice that even the h and f pawns protect each other with a classic trick of two pawns separated by one file against a king. If Kh4 f4 then white can't play Kxh5 because the f-pawn will promote. So the bishop is tied to the b-pawn promotion square and the king is tied to the h-pawn which it cannot attack. The black king is free to do whatever black likes, take the e-pawn, help support the c and b pawns or the e and f pawns.

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At 2:58 AM, Blogger Blue Devil Knight said...

Does the mate in 2 involve the knight walking over for mate, starting with Ne7?

If so, nice one. That is quite subtle.

At 8:40 AM, Blogger Loomis said...

Yep, after Kh4, white plays Ne7 and there's no way to stop Nf5#. It's very simple once you see it, but very easy to fall into.

At 1:00 AM, Blogger likesforests said...

"I believe this is not just a simple draw because of the presence of the rooks." You suspect correctly. Bishops of opposite colors endings with rooks onboard are known for being very sharp--the strategic rule is whomever takes the initiative will win because when you're on the attack, it's like having one more piece than your opponent. It only becomes drawish if you decide to trade off the rooks.


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