Tactics practice

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Christopher Kreuzer
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Re: Tactics practice

Post by Christopher Kreuzer » Sat Mar 15, 2014 10:08 pm

just returning to this thread and bumping it to see if anyone wants to try and solve the two positions above. The second one here is probably easier to work out, so I won't give the answer there just yet:

http://www.ecforum.org.uk/viewtopic.php ... 24#p133607

The first puzzle, as Roger said, is a bit of a random position, not likely to really arise in actual play. The reason I posted it was that it is possible (following the moves I gave above) to reach this position with Black to play:



Two questions:

i) Can Black queen his pawn on c2 and if not, why not?
ii) If not, what is Black's best move?

OK, part ii kind of gives away the answer to part i, but now ask yourself if you would see what is going on here if you reached this position where each player had very little time on their clock. If you were Black, would you queen the pawn and offer a draw, or queen the pawn and hope your opponent doesn't see what is going on? Or would you try and find another move?

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IM Jack Rudd
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Re: Tactics practice

Post by IM Jack Rudd » Sat Mar 15, 2014 10:42 pm

It looks really strange, but... what happens if I play 1...Qc6?

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Christopher Kreuzer
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Re: Tactics practice

Post by Christopher Kreuzer » Sat Mar 15, 2014 11:03 pm

IM Jack Rudd wrote:It looks really strange, but... what happens if I play 1...Qc6?
No idea. It looks interesting. Maybe Na4+?

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Re: Tactics practice

Post by Roger de Coverly » Sun Mar 16, 2014 12:25 am

Christopher Kreuzer wrote: but now ask yourself if you would see what is going on here if you reached this position where each player had very little time on their clock. If you were Black, would you queen the pawn and offer a draw, or queen the pawn and hope your opponent doesn't see what is going on? Or would you try and find another move?
Unless there's a mate, which I'm failing to see, you promote the pawn and ask White to demonstrate the draw, if there is one. No point in offering one, unless you fear there might be a hidden mate or you might be close to losing on time. Given the randomness, it's not a position for a plausible 10.2 claim either.

Two queens and two rooks against minor pieces, you've got a lot you can counter sacrifice before you are worse.

As that isn't a position which arises from either player trying to be solid, I'd imagine the game narrative is that one player thought they were winning, but allowed excessive counter-play

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Christopher Kreuzer
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Re: Tactics practice

Post by Christopher Kreuzer » Sun Mar 16, 2014 12:31 am

Roger de Coverly wrote:
Christopher Kreuzer wrote: but now ask yourself if you would see what is going on here if you reached this position where each player had very little time on their clock. If you were Black, would you queen the pawn and offer a draw, or queen the pawn and hope your opponent doesn't see what is going on? Or would you try and find another move?
Unless there's a mate, which I'm failing to see, you promote the pawn and ask White to demonstrate the draw [...]
Really?



Maybe have another look? White to play and win. It seems from what you say that it is easy to overlook the best move here.

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Re: Tactics practice

Post by Ian Thompson » Sun Mar 16, 2014 1:05 am

Christopher Kreuzer wrote:

Maybe have another look? White to play and win. It seems from what you say that it is easy to overlook the best move here.
Got it, but it certainly wasn't the first move I looked at. Give Roger a clue - tell him it's mate in 2.

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Re: Tactics practice

Post by Roger de Coverly » Sun Mar 16, 2014 6:12 pm

Christopher Kreuzer wrote:j The reason I posted it was that it is possible (following the moves I gave above) to reach this position with Black to play:



Two questions:

i) Can Black queen his pawn on c2 and if not, why not?
ii) If not, what is Black's best move?

OK, part ii kind of gives away the answer to part i, but now ask yourself if you would see what is going on here if you reached this position where each player had very little time on their clock. If you were Black, would you queen the pawn and offer a draw, or queen the pawn and hope your opponent doesn't see what is going on? Or would you try and find another move?

Given the hidden mate, removing the possibility with Rxg5 comes mind. Annoyingly that will control the c1 square and still threaten the mate. But it's check so it gives Black a chance to find a move. Play Rxg5 and offer a draw maybe. I don't know whether White would accept. Perhaps retake and find out what the defence to Qd8 is going to be. Qe8 by White might have to be played.

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Re: Tactics practice

Post by Christopher Kreuzer » Sun Mar 16, 2014 6:27 pm

Roger de Coverly wrote:Given the hidden mate, removing the possibility with Rxg5 comes mind. Annoyingly that will control the c1 square and still threaten the mate. But it's check so it gives Black a chance to find a move. Play Rxg5 and offer a draw maybe. I don't know whether White would accept. Perhaps retake and find out what the defence to Qd8 is going to be. Qe8 by White might have to be played.
The engines say the best defence is to run away with 1...Ka5. You get some rather strange positions after that. I suspect Black eventually wins, but am not sure (it may be drawn). My point was that this is one of those rare positions where it is entirely possible that the player of the White pieces in some situations might resign after 1...c1=Q. You call it a hidden mate - it is not really hidden as it is in plain view, just difficult to see because of the need to divert the rook that is doing the pinning, allowing the pinned piece to deliver mate (Black has two queens and a rook in the final position, but has been mated by a combination of a knight supported by a pawn, plus two bishops and self-blocks by his own queen and a pawn). I think it is entirely plausible here to see the mate, but still promote the pawn in the hope that your opponent misses the mate (offering a draw may give things away). Time trouble may play a part.

Anyway, anyone want to try the second position? It is easier, but may also just end in a draw.

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IM Jack Rudd
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Re: Tactics practice

Post by IM Jack Rudd » Sun Mar 16, 2014 6:37 pm

1...Nf2 looks like a promising start.

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Re: Tactics practice

Post by Christopher Kreuzer » Sun Mar 16, 2014 6:48 pm

That's it. The knight is completely untouchable, and Rh2+ is a massive threat. One possible reply is 2.Ne2 to cover g3. Various replies possible but 2...Ne4 looks simplest with 3.fxe4 Qxe4+ 4.Kf2 Rh2+ 5.Ke1 Qb1+ 6.Bc1 Rc8, when White can try 7.e6 to try and keep the game alive (as 7...fxe6 leaves Black's king too exposed to allow the lines previously threatened by Black), but a perpetual like 7.Rf2 Rh1+ 8.Rf1 Rh2 etc is probably the most likely outcome.

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Re: Tactics practice

Post by James Toon » Sun Mar 23, 2014 10:01 am

I was White in this position. White to play.

1. What's the best move?
2. What do you think was the plausible but inferior move that I actually played? (I won quickly, but only because my opponent blundered.)
3. (More generally) If you see a move you think is good, should you look around for something better?


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Re: Tactics practice

Post by Roger de Coverly » Sun Mar 23, 2014 10:17 am

James Toon wrote:I was White in this position. White to play.

1. What's the best move?
2. What do you think was the plausible but inferior move that I actually played? (I won quickly, but only because my opponent blundered.)
3. (More generally) If you see a move you think is good, should you look around for something better?
The immediate thoughts are that the two Candidate moves are Nb5 and Bb5 and it would be worth investing time to see if they work. Other Knight moves allow Qxa4 and I don't think Rxc8 is ever going to be enough on its own. It's a position that would have arising from the opening. I think the actual position is original, but what were the opening moves? That can sometimes help solve early problems if someone else has had a very similar position.

(edit) now spotted something. 1. Nxd5 Qxa4 2. Rxc8 Kd7 3. Nb6 check regaining the Queen and emerging with an extra pawn. But is there better? (/edit)

(edit2) It looks as if Nb6 will win, as the King cannot take the Rook on c8 and has to move away from the recapture of the Rook on c8 (/edit2)

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Re: Tactics practice

Post by James Toon » Sun Mar 23, 2014 11:15 am

On how we got here...

The opening moves were 1. d4 d5 2. c4 c6 3. Nc3 Nf6 4. e3 Bf5 5. cxd5 cxd5 6. Qb3 Qd7 7. Nf3 e6 8. Ne5 Qc7 9. Bd2 a6 10. Rc1 Nc6 11. Qa4 Rc8 12. Nxc6 Qxc6.

It isn't optimal play by either side. Black has better than 6...Qd7 followed by 7...e6, and 8. Bb5 by White is more accurate as it limits Black's options.

12. Nxc6 is a new move. I discovered afterwards that the position after 11...Rc8 had been reached once before, in Archangelsky–Del Val, World Ch Seniors 1994. The game continued 12. Nd1 Be7 13. Nxc6 bxc6 14. Bxa6 winning a pawn. White won on move 30.

After 12. Nxc6 Black can recapture 12…bxc6. Then after 13. Bxa6 the most interesting continuation is 13...Ra8 14. Nb5 Qb6 15. Rxc6 Qxc6 16. Nc7+ Kd7. Now the move order is important: 17. Qxc6+ Kxc6 18.Nxa8 loses as the knight is trapped, but 17. Nxa8 Qxa4 18.Nb6+ wins as the knight gets out and White is two pawns up.

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Re: Tactics practice

Post by Paul McKeown » Sun Mar 23, 2014 12:35 pm

Importantly, after 13. Nxd5 Qxa4 14. Rxc8+ Kd7 15. Nb6+, the Black king is driven to e7 or d6 where it obstructs the Black Bf8, allowing white to capture the Black queen without having to worry about a discovered attack against his Rc8.

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Re: Tactics practice

Post by James Toon » Sun Mar 23, 2014 6:27 pm

1. 13. Nxd5 is the best move. You have to see that Nb6+ not only forks king and queen but also forces the black king away from the rook on c8 and on to a dark square where it blocks the bishop check. This is a beautiful combination and I wish I had thought it through and played it.

2. I actually played 13. Nb5, not only skewering queen and rook on the c-file, but also threatening a double check if the queen left the a4–e8 diagonal. Black really wants to keep his queen on c6 but that's not an option. The game actually ended very quickly when Black blundered with 13…Qd7?? allowing 14. Rxc8+ winning immediately due to the impending fork on d6.

What makes 13. Nb5 inferior is that Black can sacrifice his queen with check and emerge material up: 13…Qxc1+ 14. Bxc1 Rxc1+ 15.Kd2 Rc2+ 16. Kd1 axb5. I saw this but evaluated it as better for White since I pick up the two b-pawns, I have an active queen and two connected passed pawns on the queenside, Black's king is exposed and he needs time to complete his development. However, 13. Nxd5 is a clear win.

Not 13. Bb5 because 13…axb5 14. Nxb5 Qxc1+ 15. Bxc1 Rxc1+ 16. Kd2 Rxh1 and even with the exposed king, Black has two rooks and two bishops for the queen.

3. I looked at 13. Nb5 first and decided it was good enough. I had a quick look at 13. Nxd5 but should have spent more time on it since this is a critical position and it would have been worth evaluating and comparing the candidate moves.

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