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Later Kibitzing> |
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. |
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| 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
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). |
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| 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. |
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| 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. |
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| 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? > Hi, <dzechiel>.
[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 :) |
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| 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. |
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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 |
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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. |
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| 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). |
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| 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. |
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| Feb-14-09 | | DarthStapler: I at least considered the first move but I thought black would play Nxe4 first |
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| 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 |
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| 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. |
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| Nov-20-21 | | Brenin: 17 ... Rxb2 was an obvious move, but I was undecided whether Black should play 17 ... Nxe4 first, to unleash the B on g7. Most earlier kibitzers seem to have voted for Rxb2, and I have little to add to their detailed analyses. |
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| Nov-20-21 | | mel gibson: I saw the first ply straight away
but wasn't sure of the continuation.
Stockfish 14.1 avx2 says
17... Rxb2
(17. .. Rxb2 (♖b8xb2 ♔c1xb2 ♖a8-b8+
♔b2-c1 ♕a5-a3+ ♔c1-d2 ♖b8-b2 ♖d1-b1 ♘f6xe4+ ♘c3xe4 ♕a3-a5+ ♔d2-d3 ♖b2xc2
♔d3xc2 ♕a5xa2+ ♔c2-c1 c5-c4 ♖h1-h2 ♗g7-d4 h4-h5 ♘d7-c5 ♘e4xc5 ♗d4xc5 ♖b1-b2
♗c5-a3 ♗e2xc4 ♕a2xc4+ ♖h2-c2 ♗a3xb2+ ♔c1xb2 ♕c4-b4+ ♔b2-c1 g6xh5 ♗f4xd6
♕b4-e1+ ♔c1-b2 e7xd6 ♘g1-e2 ♗c8-f5 ♘e2-c3 ♗f5xc2 ♔b2xc2 h5-h4 ♘c3-e4
♕e1-e2+ ♘e4-d2 ♕e2xd2+ ♔c2xd2) +8.57/36 161)
score for Black +8.57 depth 36. |
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Nov-20-21
 | | al wazir: I opted for 17...Nxe4 18. Nxe4 (18. fxe4 Bxc3 19. bxc3 Qa3+ 20. Kd2 Rb2 21. Rc1 Qxa2) Bxb2+ 19. Qxb2 Rxb2 20. Kxb2 Rb8+ 21. Ka1 Qa3 22. Bc1, and at that point my attack stalled. It may still be a win, but white has ♖+♗+♘ vs. ♕+♙+♙, so black has no real advantage in material. |
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Nov-20-21
 | | Gregor Samsa Mendel: Black was a great player who left us too soon, although by all accounts he lived his life to the fullest. |
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Nov-20-21
| | GoldenKnight: <Once>, I liked the way you unplugged the position. Those are the two things that jumped out at me immediately also. I first looked at Rxb2, but like you, I also would have opted for Nxe4, but <Vicao's> post was interesting. |
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| Nov-20-21 | | agb2002: The DSB and the rook on b8 converge on b2. This suggests 17... Rxb2, followed by either Nxd5, Nxe4 or Nxg4 depending on the position. For example, 18.Qxb2 Nxe4 (18... Nxd5 19.Rxd5 clears d1 for the white king) 19.fxe4 (19.Rd3 Nxc3 looks winning) 19... Bxc3 20.Qb3 Rb8 21.Bc4 (21.Qc2 Qa3+ 22.Qb2 Qxb2#) 21... Rxb3 22.Bxb3 c4 23.Bxc4 Qa3+ 24.Kc2 Qb2+ 25.Kd3 Nc5+ 26.Ke3 Bxg4 looks very good for Black. Or 18.Kxb2 Rb8+ 19.Kc1 (19.Ka1 Nxe4 is winning) 19... Qa3+ 20.Kd1 Rb2 recovers the material while keeping the attack. Or 18.Qd3 Qa3 19.Nb1 Rxb1+ 20.Kxb1 Rb8+ wins decisive material. |
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Nov-20-21
 | | scormus: Hmmmm, a very Dragonesque position.
I wondered about 17 ....Rxb2 (18 Kxb2 Rb8+ etc), but .... Nxe4 looked so natural that I felt that should come first.
I see my engine preferred the R-sac immediately, but didn't eval much difference between them.It almost looks like it will soon be over after 19 ... Qa3+, but B's forces are very committed to the attack and a bit more work needed. I would never have got whole sequence, and could see myself messing it up playing OTB |
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| Nov-20-21 | | saturn2: 10. 0-0-0 seems a 1600 player move |
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Nov-20-21
 | | chrisowen: Enter dragon i v Rxb2 flick arrive i sack flubb publish enter dragon i v mc v grinch i v hicky vicky avid jaybird davos question quotas evict blip went wenceslas frazzle u it cue it al o v hormones v gideon i avid signed it why tow it z o v it swamp yes v bobs bubble farm choo choo it gave it adagio it nag huck ointment v arrived oddly jobs awooga it head roof aint hang fan v no info flicker dig gideon huge jain i japs sit was lugger aids v hest noon ro kite v i nahback caddy paced it cushioned it right v i c force haggle bids v bigs foot c weed it out knight v walkin danced it safe gank hent jail theign nips cringed frig i v defines cracked hide jivers jack doot fizz woosh cajole v i zack q gook brag toot geriatric v i reckon gramps frig i v sticky avid it was wicket hellgate i v knight asker accident & emergency parse it no v mandy c lassoo o phone in home it Rxb2 daffy; |
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Nov-20-21
| | chrisowen: Having mix up no? |
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| Nov-20-21 | | AlicesKnight: I looked at ....Rxb2, ....Nxd5/e4, ....Rab8+ and ....Q check in some sort of order without finding the best sequence. White has castled 'into it' and with his KR and KN idle looks to be in "nid". |
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Nov-20-21
| | Jimfromprovidence: I missed the lethal implications if 19 Ka1 followed by 19...Nxe4, below, pinning the knight. 
click for larger viewIt's the threat of 20...Qxc3+ 21 Qxc3 Bxc3# |
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Later Kibitzing> |
Kibitzing
sac: 17...Rxb2