< Earlier Kibitzing · PAGE 2 OF 2 ·
|Feb-14-09|| ||goodevans: <Once: Like <Dzechiel> I wanted to play Nxe4 rather sooner than in the game, but I don't think it affects the outcome much.>|
... but it has the merit of eliminating the possibility of white recapturing with Nxe4.
|Feb-14-09|| ||Samagonka: Oops! So it said Black to play?|
|Feb-14-09|| ||onesax: <fouard> sorry, of course it was a typo. I meant fxg4. I didn't feel the need to waste a post earlier to correct myself, because I felt it would be obvious, and unnecessary. :S|
|Feb-14-09|| ||whiteshark: I calculated <17…Rxb2 18.Kxb2 Rb8+ 19.Kc1 Qa3+ 20.Kd2 Rb2 21.Rc1 Rxc2+ 22.Rxc2> and thought it should win in the long run.|
|Feb-14-09|| ||Oliveira: Hey, guys! Could you tell me what was the puzzle of yesterday?|
|Feb-14-09|| ||Woody Wood Pusher: I saw it most of it, wouldn't have gone for this OTB though.|
|Feb-14-09|| ||agb2002: Two black pieces converge on b2 and c3. The black KN has six legal moves to unblock the DSB but I have considered only 17... Nxg4 (threatening 18... Nf2 and 18... Rxb2) 18.fxg4 Rxb2:|
A) 19.Qd3 Bxc3 and Black is two pawns up and has a crushing attack (threatens ... Qxa2).
B) 19.Qxb2 Bxc3
B.1) 20.Qc2 Qa3+ 21.Kb1 Rb8+ and mate soon.
B.2) 20.Qb1 Rb8
B.2.a) 24.Qxb8 Nxb8 25.Kc2 (25.Bc4 Bxg4) Bf6 and White will lose another pawn.
B.2.b) 24.Qb3 Rxb3 25.axb3 Qa1+ 26.Kc2 Qb2+ 27.Kd3 Qxb3 .
B.2.c) 24.Qd3 Qa3+ 25.Kc2 Qb2#.
B.3) 20.Qb3 Rb8 is similar to B.2).
C) 19.Kxb2 Rb8+
C.1) 20.Qb3 Qxc3+ 21.Ka3 (21.Kb1 Rxb3+ 22.axb3 Qb2#) Qa5+ 22.Qa4 Bb2#.
C.2) 20.Ka1 Qxc3+ 21.Qxc3 Bxc3#.
C.3) 20.Kc1 Qa3+ (20... Bxc3 21.a4) 21.Kd2 Rb2
C.3.a) 22.Rc1 Qxc3+ 23.Kd1 Rxc2 24.Rxc2 Qd4+ followed by ... Qxe4 with Q+3P vs. 2R.
C.3.b) 22.Nb1 Qb4+ 22.Ke3 (22.Kd3 Qd4#; 22.Nc3 Qxc3+ 23.Kc1 Qxc2#) Rxc2 .
Time to check.
|Feb-14-09|| ||whiteshark: <Oliveira> Piket vs Gulko, 1990
|Feb-14-09|| ||Oliveira: Thank you, whiteshark!|
|Feb-14-09|| ||agb2002: I didn't even consider 17... Rxb2 because I felt it required some preparation. The text move is more forcing than 17... Nxg4 but I think that this is enough to win. Would anybody try some computer ply crunching?|
|Feb-14-09|| ||Once: <Oliveira: Hey, guys! Could you tell me what was the puzzle of yesterday?>|
<whiteshark> has given you yesterday's puzzle. If you ever need to know again, just take a look at the profile of one of the regulars. We're pretty much here every day. It shouldn't be too hard to find a previous puzzle that way.
|Feb-14-09|| ||blacksburg: Rxb2. first move i looked at, and it worked out!
no way i would see this in a real game, though.
|Feb-14-09|| ||beenthere240: It looks like a very delayed Benko (b5 postponed to move 10), with all of the typical attack elements -- sac on B2 from the opened b file, Qa5, discovered attack from the g7 bishop with a knight move from f6. If you aren't looking for moves like 17...Rxb2 from the outset, you shouldn't go into this line.|
|Feb-14-09|| ||johnlspouge: Saturday (Very Difficult)
Petursson vs Wojtkiewicz, 1990 (17...?)
Black to play and win.
Material: Even. The White Kc1 has 2 legal moves. The Black Rb8 is on a semi-open file, with Ra8 able to reload. The Black Bg7 is aimed at Pg7, a tender point in the White K-position, with the White Nc3 and Black Nf6 in between. The Black Qa5 attacks Nc3 and Pa2. The Black Bc8, Nd7, and Nf6 require activation. The Black Kh7 is presently secure. No White piece is obviously overburdened or loose, so an examination of forcing moves (checks, captures, and threats) is next.
Candidates (17…): Rxb2
White must capture or drop a P without compensation. He has 2 possible captures.
(1) 18.Kxb2 Rb8+
(1.1) 19.Kc1 Qa3+ 20.Kc2 Rb2
Black gains Q+P for 2Rs and has the better position because the White Kc2 is exposed.
(1.2) 19.Ka1 Nxe4 (threatening 20…Bxc3)
White cannot capture Ne4 without being mated, so Black regains the material and retains Ka1 in a hideous crossfire from Rb8 and Bg7. Thus, White must give back material to close the b-file.
(1.3) 19.Bb5 [Nb5 Nxe4+] axb5 (threatening 20…b4 21…Nxe4+)
White must get Kb2 off the long diagonal.
20.Kb1 b4 (threatening 21…b3 22.axb3 Nxd5 then 23…Qa1#)
Clearly, the White K-position is opening up, with no relief in sight.
(2) 18.Qxb2 Rb8 19.Qa1 [Qxb8 Qxc3+ 20.Kb1 Nxb8]
Variations after 19.Qc2, 19.Qd2, 19.Bb5 are similar to Variation (1).
19…Nxe4 (threatening 20…Bxc3 trapping Qa1)
In Variation (2), the White Qa1 is helpless as Ka1 was in Variation (1). White cannot capture Ne4 without dropping Q+2P for R+B, so Black regains the material and retains Ka1 in the same crossfire as in Variation (1).
|Feb-14-09|| ||zb2cr: I went straight for 17...Nxe4 instead of 17. ... Rxb2, with the Rook capture to follow. I think it might transpose after 18.fxe4, Rxb2; 19.Kxb2, Rb8+ etc.|
|Feb-14-09|| ||johnlspouge: < <agb2002> wrote: I didn't even consider 17... Rxb2 because I felt it required some preparation. The text move is more forcing than 17... Nxg4 but I think that this is enough to win. Would anybody try some computer ply crunching? >|
Hola, <agb2002>. At a Mom-and-Pop 15 plies, Toga II 1.3.1 agrees with your evaluation. The last move I entered is <emphasized>. (Humans can improve near the end of the complete computer variations I give.)
[ply 15/51 time 00:41 value (to White) -1.48]
17…Nxg4 18.fxg4 <Rxb2> 19.Kxb2 Rb8+ 20.Kc1 Qa3+ 21.Kd2 Rb2 22.Rh3 Nf6 23.Qxb2 Qxb2+ 24.Ke1 Nxg4 25.Bd2 Nf2 26.Kxf2 Bxh3 27.Nxh3 Bxc3 28.Bxc3 Qxc3 29.Nf4 Qc2 30.Ke3 Qxa2
[ply 15/59- time 01:28 value (to White) -3.30]
17…<Rxb2> 18.Kxb2 Rb8+ 19.Kc1 Qa3+ 20.Kd2 Rb2 21.Rb1 Nxe4+ 22.Nxe4 Rxc2+ 23.Kxc2 f5 24.gxf5 gxf5 25.Bd3 c4 26.Ng5+ hxg5 27.Bxf5+ Kg8 28.Bxg5 Qxa2+ 29.Kd1 Qg2 30.Be6+ Kf8 31.Bxd7 Bxd7 32.Rb8+ Kf7
At this point, generally out of irritation with superficial analysis, I often say that my CG chessforum contains detailed instructions on downloading Toga, which is freeware.
On the other hand, <agb2002>, your thoughtful analysis is always a pleasure to read. I am more than willing to run an occasional computation at your request. Many thanks.
|Feb-14-09|| ||johnlspouge: < <dzechiel> wrote: Our line differs slightly from the text in that we wanted to play ...Nxe4 earlier. We don't know if this is significant or not. <MAJ> is this a big deal? >|
[ply 15/49 time 00:33 value (to White) -1.36]
17…Rxb2 18.Kxb2 <Nxe4> 19.fxe4 Rb8+ 20.Kc1 Qa3+ 21.Kd2 Rb2 22.Rh3 Nf6 23.Qxb2 Qxb2+ 24.Ke1 Nxg4 25.Bd2 Nf2 26.Kxf2 Bxh3 27.Nxh3 Bd4+ 28.Kf1 Bxc3 29.Bxc3 Qxc3 30.Nf4 c4 31.Rb1
[ply 15/53 time 02:04 value (to White) -3.32]
17…Rxb2 18.Qxb2 <Nxe4> 19.a4 Nxc3 20.Qa3 Nxd1 21.Kxd1 Rb8 22.Bd2 Rb1+ 23.Kc2 Qb6 24.h5 gxh5 25.Bc3 Bxc3 26.Bd3+ Kg8 27.Kxc3 Qa5+ 28.Kc2 Qe1 29.gxh5
Comparison with my previous computation for <agb2002> indicates that the alternatives to 17...Rxb2 18...Rb8 are much inferior, but the ones suggested are winning.
I am not going to give <you> my spiel about downloading Toga, David. This site needs its purist :)
|Feb-14-09|| ||euripides: I guess when playing 17...Rxb2 Wojkiewicz saw as far as move 25 and that if the white knight moves on move 25 Black has 25...Qa4+ winning the f4 bishop. He might just have seen to move 21, but that position wouldn't look very promising for Black if Nxe4 didn't work.|
|Feb-14-09|| ||Jimfromprovidence: I have a query. If white plays 17 Bd3, below, (to discourage Nxe4), can 17...Rxb2 still work?|
click for larger view
|Feb-14-09|| ||playground player: <Once> Thank you for a very illuminating kibitz! I couldn't find the solution to this puzzle on account of all the underbrush on the chessboard: but you have cleared it away, and now the solution stands out boldly.|
|Feb-14-09|| ||crwynn: I figured 17...Ne4, which is actually winning too, but only after 18.fe Rb2 19.Kb2 Rb8 20.Kc2 Qa3 (instead I looked at 20...Bc3, but after 21.Rd3 Black may not have quite enough for the rook).|
|Feb-14-09|| ||A.G. Argent: <Dr.JohnLSpouge> <dzechiel...this site needs it's purist.> John, very well said. It truly does. And in particular, one like David Z.|
|Feb-14-09|| ||DarthStapler: I at least considered the first move but I thought black would play Nxe4 first|
|Feb-14-09|| ||Vicao: My variation started with Nxg4 too, but after fxg4 this has opened the 3rd rank for white to defend his c3-knight with Rh3 at the end.... That was a resource that i missed completely|
|Feb-14-09|| ||patzer2: For today's difficult, Saturday, Feb 14, 2009 (Valentine's Day) puzzle solution, Black's sham sacrifice 17...Rxb2!! demolishes White's weak Queen-side castled position to enable the win of decisive material. |
See <johnlspouge>'s Toga analysis above for a winning follow-up line.
< Earlier Kibitzing · PAGE 2 OF 2 ·