Tactical vision

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Christopher Kreuzer
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Tactical vision

Postby Christopher Kreuzer » Sat Feb 04, 2012 3:10 pm

Since posting variations within a pgn doesn't seem to be possible, I'm only going to post a position that is a variation from a game I played on Thursday evening. I wouldn't normally do this (post positions from my games), but the game itself was a bit crazy (I was White and sacrificed a whole rook on move 11) and both the game and looking at the variations afterwards reminded me why I play chess!

The following position could have arisen after Black's 17th move. In the game, I played 17.Bb2+ instead of using the bishop on d3 to capture the Black queen on e4, and this variation arose after considering what to do after 17.Bxe4 if Black had played 17...h5.

[FEN "rn3r2/pbpp1pk1/1p4p1/2PP3p/4B1N1/P7/2PP1PPP/2B2RK1"] [SetUp "1"] *

As you can see, I've regained a piece for the sacrificed rook, so am 'only' the exchange down for a pawn. The question is quite simple. What is White's best move here? The computer flashed up the answer almost immediately, but it left me looking at the screen wondering whether the silicon monster had gone temporarily insane. The move is, in fact, remorselessly logical, but you have to have real vision to see it. I'm not ashamed to say I would never have seen it in a million years. :D

Anyone see what the move is?

Paul Cooksey

Re: Tactical vision

Postby Paul Cooksey » Sat Feb 04, 2012 3:27 pm

Christopher Kreuzer wrote:Anyone see what the move is?
It's pretty easy after someone has told you there is a tactic there. :)

A standard problem, finding the move in a problem very much easier than seeing it in a game a couple of moves ahead.

Jonathan Rogers
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Re: Tactical vision

Postby Jonathan Rogers » Sat Feb 04, 2012 4:19 pm

Not sure about the answer. Maybe 1 Nf6 hoping for 1...Kf6 2 Bb2+ Kg5 3 Bg7! with a mating net; and 2...Ke7 3 d6 wins back all the sacrified material and I suppose that White is somewhat better in the resulting position. But am I supposed to be looking for more?

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Christopher Kreuzer
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Re: Tactical vision

Postby Christopher Kreuzer » Sat Feb 04, 2012 4:25 pm

Paul Cooksey wrote:
Christopher Kreuzer wrote:Anyone see what the move is?
It's pretty easy after someone has told you there is a tactic there. :)

A standard problem, finding the move in a problem very much easier than seeing it in a game a couple of moves ahead.


Thank-you for not posting what you think the move is. I wonder, though, how we will know if you were right or not! 8) I wonder if Carl could magic up something where people can post sealed answers somewhere (I don't really want to get loads of PMs with people saying what they think the move is. I suppose this is why posting tactical positions like this doesn't really work very well. Are there applications out there where you can offer up positions and people make a move on the board and get told whether they are right or wrong?

PS. Jonathan Rogers just posted the answer! So now you can tell us if you saw that.

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Christopher Kreuzer
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Re: Tactical vision

Postby Christopher Kreuzer » Sat Feb 04, 2012 5:07 pm

Jonathan Rogers wrote:Not sure about the answer. Maybe 1 Nf6 hoping for 1...Kf6 2 Bb2+ Kg5 3 Bg7! with a mating net; and 2...Ke7 3 d6 wins back all the sacrified material and I suppose that White is somewhat better in the resulting position. But am I supposed to be looking for more?


Not much more than that. You do have to have a reason for playing 1.Nf6 instead of 1.Ne3 and have a response ready for 1...bxc5 - i.e. what compensation do you have for the exchange? FWIW, my ancient chess engine assessed that position as level, though give it a bit longer and it might change its mind.

The main line after 3.Bg7 is 3...Kf4 (forced). I found it hilarious that with nothing more than two bishops White by playing 3.Bg7 is able to force the Black king to flee up the board to its doom. One line where White gives up nearly all his remaining material (though he doesn't need to) is: 1.Nf6 Kxf6 2.Bb2+ Kg5 3.Bg7 Kf4 4.Re1 Rg8 5.g3+ Kg4 6.Bf3+ Kxf3 7.h3 Rxg7 8.Re3#

There are some nice variations in the other lines as well: 1.Nf6 Kxf6 2.Bb2+ Ke7 3.d6+ Ke6 (if 3...cxd6 4.Bxb7 Nc6 5.Re1+ Kd8 6.cxd6 and the threat of 7.Bf6+ is brutal) 4.Bxb7 Nc6 5.Re1+ Kf5 (if 5...Kd5 6.Re5+ [the c6 knight is pinned by the bishop on b7] 6...Kc4 7.Ba6+ b5 8.d3# is just jaw-dropping, though I only just figured out that line from looking at the screen so if it's wrong that will be embarrassing...) 6.Bxc6! (far superior to taking the rook, though as Jonathan noted, that wins as well) 6...dxc6 7.Re5+ and now, humiliatingly, Black is forced to play into the rook and bishop battery by 7...Kf6 as moving the king to f4 or g4 is another mating net. Then White just plays 8.Rxh5+ and 9.Re5+ and 10.dxc7 and is winning.

I guess what I've learnt from this is that if you drag the opposing king far forward enough, and you have your three pawns on their original squares in front of your castled king, and then manage to block off the king's retreat, that will often be enough for a mating net.

Anyway, that mating net on the other side of the board that ends with 8.d3#

[FEN "r4r2/p1pp1p2/B1nP2p1/1pP1R2p/2k5/P2P4/1BP2PPP/6K1"] [SetUp "1"] *

Michael Jones
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Re: Tactical vision

Postby Michael Jones » Sat Feb 04, 2012 7:02 pm

I guessed 18. Nf6 purely on the basis that it looked the stupidest move possible, which was probably why you'd posted it. There's no way I could have calculated all the variations!

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JustinHorton
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Re: Tactical vision

Postby JustinHorton » Sat Feb 04, 2012 7:17 pm

"Do you play chess?"
"Yes, but I prefer a game with a better chance of cheating."

lostontime.blogspot.com

Jonathan Rogers
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Re: Tactical vision

Postby Jonathan Rogers » Sat Feb 04, 2012 7:34 pm

yes P v P helped me to see 2...Kg5 3 Bg7 quickly. It seems that White's position is better than I thought after 2 Bb2 Ke7 though. After 1 Nf6 bxc5 surely 2 Bb2 more or less paralyses Black. The "purpose" of Nf6 is to paralyse Black with the follow up of Bb2, and to my mind the main feature of the position was that this has to be done via this move order rather than by 1 Bb2+ which allows ...f6.

One of my main chess regrets is not having the time (or even equipment!) to run my own games through computers.

E Michael White
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Re: Tactical vision

Postby E Michael White » Sat Feb 04, 2012 7:53 pm

1.Nf6 Na6 2.Bb2 Nxc5 should give Black a draw too. Na6 is one of those moves strong players tend to play just when you think you are winning.

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Christopher Kreuzer
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Re: Tactical vision

Postby Christopher Kreuzer » Sat Feb 04, 2012 10:30 pm

JustinHorton wrote:Petrosian-Pachman


Thanks for that. I'm copying that game here (hopefully that is OK, it's not every day you find out that a variation from one of your games included a tactic similar to one played by Petrosian):

[Site "It Bled"]
[Date "1961"]
[Result "1-0"]
[White "Petrosian"]
[Black "Ludek Pachman"]
[ECO "A04"]
[PlyCount "42"]

1.Nf3 c5 2.g3 Nc6 3.Bg2 g6 4.O-O Bg7 5.d3 e6 6.e4 Nge7 7.Re1
O-O 8.e5 d6 9.exd6 Qxd6 10.Nbd2 Qc7 11.Nb3 Nd4 12.Bf4 Qb6
13.Ne5 Nxb3 14.Nc4 Qb5 15.axb3 a5 16.Bd6 Bf6 17.Qf3 Kg7 18.Re4 Rd8 19.Qxf6+
Kxf6 20.Be5+ Kg5 21.Bg7 {1-0}

I have a new-found respect for how a rook and bishop pair can weave mating nets. The only ways to avoid the threat of h4+ and Bh3/f3# are Nf5, Kf5 and e5, all three moves allowing mate in three. (EDIT: Correction: Kf5 allows mate in 2 actually...)
Last edited by Christopher Kreuzer on Sun Feb 05, 2012 1:32 pm, edited 1 time in total.

Ian Kingston
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Re: Tactical vision

Postby Ian Kingston » Sun Feb 05, 2012 12:32 pm

From one of my own games:

[FEN "8/2r1b1p1/5pkp/2p2R2/1pBpP1PP/3P4/PP6/6K1 w - - 0 37"] [SetUp "1"] *

I missed Bg8, winning a pawn, here and on the next move.


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