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Dec-10-10 gmalino : Happy birthday cgc, thanks for your great work! Always a pleasure to come to your site.

Dec-10-10 TheBish : V Cmilyte vs E Boric, 2008 White to play (23.?) "Difficult"

I assumed that the winning idea here would make use of the latent pin of Black's queen against her king, possibly sacrificing the white queen for checkmate. Turns out, my hunch was correct. 23. Nxc6!

This clears the path for the bishop on a1, which is a key player. Now Black has three replies, all losing: A) 23...Qxc6? 24. Rd8+! (much better than winning the queen with Rd6+ or Rc5+) Kg8 25. Rxf8#. B) 23...bxc6 24. Rd7! Qxb3 (other moves also lose, like 24...Re8 25. Rxg7+ or 24...Qf7 25. Rxf7) 25. Rxg7+ Kh8 26. Rxg6+ and mate in a couple. C) 23...Bxa1 24. Nd8!

This was the hardest line for me to find. In this line, White tries to drive the queen off the a2-g8 diagonal to give a wicked discovered check. 24...Rxd8

Otherwise, White will win the queen with a discovered check -- there's no place to hide! 25. Rxd8+ Kf7 26. Rf8+! Ke8 27. Re8+ Kxe8 28. Qxe6+ with an easy win.

Dec-10-10 Oxnard : 23. Nxc6 then 23. … Qxc6 loses to Rd6+, so bxc6 but then 24. Rd7! and if Qxb3 25. Rxg7+ Kh8 26. Rxg6+ Rf6 27. Bxf6#. Hence 23. … Bxa1 only move but then 24. Nd8! looks very strong as it knocks the black queen off her king's diagonal, allowing the deadly revealed check (sacrificing the exchange loses very quickly too eg. 24. … Rxd8 25. Rxd8+ Kf7 26. Rf8+ Ke7 27. Re8+) for which I can safely declare winning without further analysis.

Dec-10-10

agb2002 : White is a pawn ahead.

Black threatens 23... Nxe5 and 23... Nxb4.

If the white knight disappeared then 23.Rd7 Re8 (or 23... Rf6; 23... Qxb3 24.Rxg7+ Kh8 25.Rxg6+ and mate in three) 24.Qxe6+ Rxe6 25.Rxg7+ Kf8 26.Rxb7 Rxe2 27.Bf6 and White should win the endgame. Therefore, 23.Nxc6: A) 23... bxc6 24.Rd7

A.1) 24... Qxb3 25.Rxg7+ Kh8 26.Rxg6+ and mate in two. A.2) 24... Re8 25.Rxg7+ Kf8 26.Qc3 + - [B+P].

A.3) 24... Rf6 25.Rxg7+ Kf8 (25... Kxg7 26.Qxe6) 26.Qxe6 Rxe6 27.Rxb7 Rxe2 28.Bd4 + - [B+P]. B) 23... Bxa1 24.Nd8 Rxd8 (otherwise the discovered check wins the queen) 25.Rxd8+ Kf7 26.Rf8+ Ke7 27.Re8+ wins. C) 23... Kh8 24.Rd8

C.1) 24... Qxb3(xc6) 25.Rxf8#.

C.2) 24... Rxd8 25.Bxg7+ Kxg7 26.Qxe6 + -.

C.3) 24... Qf7 25.Qxf7 + -.

D) 23... Ra8 24.Rd8+ and 25.Qxe6+ wins.

E) 23... Kf7 24.Rd7+ wins.

Dec-10-10 gofer : White has created two threats, one along the a2-g8 diagonal and one along the a1-h8 diagonal. Both are real and verifiable. However, Bg7 and oir own Ne5 is blocking one and Qe6 and our own Rd5 is blocking the other. Now Re5 is actually all part of the plan, because of the discover check threat, but this only works if Re5 moves and gives check! However this can happen in two ways; 1) Qe6 moves off the diagonal, 2) Rf8 captures on d8 and we then recapture on d8 with Rxd8+! 23 Nxc6 ...

Option 1 (ignore the threat on the a1-h8 diagonal)

++++++++++++++++++++++++++++++++++++++

23 ... bxc6

24 Rd7! Qxb3 (Qd5 and Qf7 don't help)

25 Rxg7+ Kh8

26 Rxg6+ mating

Option 2 (ignore the threat on the a2-g8 diagonal)

++++++++++++++++++++++++++++++++++++++

23 ... Bxa1

24 Nd8! Queen anywhere but f7 (Rxd8 Rxd8+ winning)

25 Re5 moves to attack the queen where ever it is now 25 Rc5+ (for 24 ... Qc8) winning

25 Re5+ (for 24 ... Qe8/Qe7/Qxe2) winning

25 Rxf5+ (for 24 ... Qf6) winning

Now there are other options where black ignores both diagonals! But these are so bad that I am not going to look at them! (i.e. 23 ... Qxc6 24 Rd7+ etc) Time to check.

Dec-10-10 gofer : Two days in a row where I have missed another defensive option! 24 Kh8 accepting loss of the knight is an option given the two alternatives, but after... 23 ... Nxc6

24 Kh8 Bxg7+

25 Kxg7 Nd4

White is a full knight up and a pawn up, so is losing badly, but that is still better than being mated or losing our queen!

Dec-10-10 David2009 : V Cmilyte vs E Boric, 2008 White 23? 23 Nxc6 seems to win quickly, main variation 23...bxc6 24 Rd7 Qxb3 25 Rxg7+ Kh8 26 Rxg6+ and mate in two. I have seen similar mates before but not this particular game. Time to check the game and see if Crafty End Game Trainer can find anything better for Black:

=====

In the puzzle position there is nothing better than the game line. In the resignation position Black can struggle on a piece down with 24...Rf6 etc. Rewind instead to the previous move:



click for larger view (V Cmilyte vs E Boric, 2008 White 22?) After 22 Rxd5, Qe6?? is a blunder, instead 22...Qxg4 gives Black at least equality. If Black can unravel and exchange Rooks, his passed Pawn will become very strong. To my surprise and pleasure, I managed to draw as White first time against Cragty EGT (link http://www.chessvideos.tv/endgame-t...). Perhaps I am getting better.

Dec-10-10 knight knight : White's a pawn up. Ok about ten minutes of thinking and I reckon 23. Nxc6 might be the move: a) 23...Qxc6 24. Rd6+ Kh8 25. Rxc6 winning

bi) 23...bxc6 24. Rd7 Qxb3 25. Rxg7+ Kh8 26. Rxg6+ mating bii) 23...bxc6 24. Rd7 Re8 25. Rxg7+ winning material c) 23...Bxa1 24. Nd8 will win the queen via discovered check, e.g. 24...Qe7 25. Rd7+ Kh8 26. Rxe7 Rxd8 27. Qf7 is actually mate soon d) 23...Kh8 24. Bxg7+ Kxg7 nope, let's try 24. Nd8 again. 24...Qe7 25. Bxg7+ Kxg7 (25...Qxg7 26. Ne6 Qa1+ 27. Kg2 remains a piece and pawn up) 26. Qd3 retains the piece and threatens 27. Rd7 pinning the queen e) 23...Re8 24. Nd8 Qe7 25. Bxg7 essentially the same as line d) There may be other defences, time to check...

Dec-10-10 Boerboel Guy : Got it... and the Nd8 move!

Found the puzzle quite easy for a Friday.

Dec-10-10 desiobu : I was way off track. I looked at Nf3 with the idea of Ng5, controlling e6 and f7, and preparing an exposed check with the hopes of winning the queen but h6 (or maybe something even better) pretty much ends that.

Dec-10-10 timothee3331 : <dzechiel> <but this leaves black down an exchange and a pawn with no other compensation.> actually after 25...Kf7 26.Rf8+ Ke7 27.Re8+ Black loses more than the exchange ^^ (though the exchange would be highly sufficient !)

Dec-10-10 Patriot : My candidates were Nxg6 and Nxc6. 23.Nxg6? Qxg6 24.Rd7+ and black has the opportunity to play into a pin with 24...Rf7 or allow material trades after 24...Kh8 25.Rxg7 Qxg7 26.Bxg7+ Kxg7 which all looks hokie for white. 23.Nxc6 looks far better. A) 23...bxc6 24.Rd7 Qxb3 25.Rxg7+ Kh8 26.Rxg6+ and mates. B) 23...Bxa1 24.Nd8! Rxd8 25.Rxd8+ Kf7 26.Rf8+ Ke7 27.Re8+ C) 23...Qxc6 24.Rd6+ at least wins the queen.

--------

After going over the comments, there are several possible defenses I missed. <agb2002> shows several more possibilities within variation A (24.Rf6 and 24.Re8) which he refutes accurately. His variation C of 23...Kh8 is interesting because I rarely look at possibilities where a capture is simply ignored. Most of the time this results in dropping material for no compensation. In this case it is true the knight on c6 is about to be re-captured and this gives white the flexibility to move it to safety and be a piece up or ignore it and play another useful move (which he does) since if black re-captures then white isn't really down anything. Variations D & E also ignore the capture. Variation D (23...Ra8) is interesting--it does threaten 24...Rxa1+. Variation E (23...Kf7) attempts to protect the queen but loses as he points out. I sometimes use <agb2002> 's analysis as a way of making sure I'm not missing any critical candidates because if there are any, you can be sure he will find them!

Dec-10-10

patzer2 : As <Knight Knight> mentions, 23...Bxa8! creates the decsive threat to win the Queen with a discovered check. However, there are two other amusing possibilities:

If 23...Bxa8 24. Nd8! Rxd8, then 25. Rxd8+ Kf7 (diagram below)

click for larger view 26. Rf8+! Ke7 26. Re8+ Kxe8 27. Qxe6+ picks off the Queen with a deflection (removing the guard or defender) tactic. If 23...Bxa8 24. Nd8! Qxe2 (diagram below)



click for larger view White can win the Queen with the discovered check with 25. Qd2+ or 25. Qe5+. However, even stronger in this position is 25. Rxf5+! with a mating attack after 25...Kg7 26. Rxf8 Qe1+ 27. Kg2 Qe4+ 28. Kh3 Kh6 29. Qg8 with a decisive mate threat (e.g. 29...Qe7 30. Nf7+ Kh5 31. Qxh7#).

Dec-10-10

paulalbert : Took a little while to make sure I got all variations but got this one;not bad for a 1400 player. Once you see the idea, the lines are reasonably forcing and calculable. You have to change from thinking about winning the Black pinned Queen to giving up your own. Nice combination by Victoria.

Dec-10-10

kevin86 : I missed this one. The simple exchange got the knight out of the way and set the stage for the queen sac that leads to mate (sorry,the windmill is not good enough). 24 ♖d7!! ♕xb3 25 ♖xg7+ ♔h8 26 ♖g6 dis+ and mate in two more moves

Dec-10-10 Patriot : <paulalbert> <Took a little while to make sure I got all variations but got this one;not bad for a 1400 player. Once you see the idea, the lines are reasonably forcing and calculable. You have to change from thinking about winning the Black pinned Queen to giving up your own.> You're probably under-rated. There are a number of themes hidden in this, stemming from the queens and black king aligned on the diagonal. In some lines, it is possible to sac the queen to deliver mate using the bishop and rook. Another theme is the discovered check, a pin, and removal of the guard. Nd8 is another theme (which I can't remember at the moment) to chase the queen to a square where a discovered check and at least winning the queen becomes possible. Your profile is very interesting!

Dec-10-10 scormus : <paulalbert: Took a little while ...> Took me a while too. It would have been quite easy to miss but I was sure it was along the lines you said .... 1400 must be a better standard than I realised.

Dec-10-10 BOSTER : <Phony Benoni> <I expect other 23.N-moves to be in investigated> . < desiobu> <I looked at Nf3 but h6> 23.Nf3 h6 24.Bxg7 Kg7 25.Re7 and white wins. I guess Nf3 is winning too.

Dec-10-10

Sastre : <BOSTER> After 23.Nf3, Black has 23...Ne7 24.Bxg7 Qxd5 25.Qxd5+ Nxd5 26.Bxf8 Kxf8 27.b5 Ke7 =.

Dec-10-10 wals : Yes, got 23.Nxc6, but that's about all.

Rybka 4 x 64 - blunders only

depth: 25 : 5 min :

Black blunder

(+6.12):22...Qe6. Best, Qxb4, +0.79.

23.Rd7, +6.50. and black resigned.

Dec-10-10

Domdaniel : Saw 23.Nxc6 bxc6 24.Rd7 Qxb3 25.Rxg7+ mating, then noticed black could spoil the fun with 23...Bxa1. But 24.Nd8 seems to do the trick. The WQ has nowhere to hide ... Any other wrinkles? Nothing too serious, I hope.

Dec-10-10

Phony Benoni : After <BOSTER> 's suggested 23.Nf3:

click for larger view <Sastre's> line beginning with 23...Ne7 certainly gives Black good chances for a draw. 23...h6 is tricky. Black looks like he's innocently stopping 24.Ng5, but there are other points. If White tries 24.Bxg7 Kxg7 25.Rd7+??, Black wins with 25...Qxd7 since his king had walked out of the pin. Also, after 23...h6, 24.Rd7 Qxb3 25.Rxg7+ Kg8, there's no mate because Black now has a flight square on h7. Worse yet, White doesn't have a discovered check to recover the queen, so he would have to settle for perpetual check. However, after 23...h6 24.Bxg7 Kxg7 White could simply play for the win with his extra pawn, as he could have done without all this folderol. So 23...Ne7 is clearly the safer move. While the basic ideas are the same, Nf3-g5 is not as forcing as Nxc6-d8. By capturing on c6, White cuts Black's options down to three: (1) recapture on c6; (2) try ...Bxa1; (3) play a piece down. Black has a lot more latitude after 23.Nf3; besides 23...Ne7, he can avoid the worst with 23...h6, 23...Kh8, or even 23...Bxa1.

Dec-10-10 Blunderdome : The critical line is definitely 23. Nxc6 Bxa1 24. Nd8

Dec-10-10

tpstar : Accepting the Queen sacrifice leads to a Morphy Concealed Mate featuring a brief Windmill before the Bishop mates on the long diagonal. The running list = Nimzowitsch vs B Nielsen, 1930

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