13 September 2015

Commentary: 2015 U.S. Championship, Round 10 (Nemcova - Paikidze)

I'll finish off my commentary on selected games from the 2015 U.S. Championship with the round 10 game featuring Katerina Nemcova (whose round 9 game was previously featured) and Nazi Paikidze (whose games in round 7 and round 8 were also examined). White in this game avoids the line in the Classical Caro-Kann (11...a5!?) that Paikidze used in round 8, instead deviating early with the interesting sideline 6. Nh3.  This has some aggressive potential, as shown by the 9. f4 advance, but White is a bit slow to develop and Black equalizes by the early middlegame. After that it is a strategic war with tactical undertones, as the position's pawn structure and minor pieces are significantly imbalanced.  Eventually White overreaches and Black calculates well to find a defense while waiting to execute her game-ending mate threat.

For Caro-Kann players of either color, this game holds a lot of interest, since a number of typical themes appear.  The results of the f-pawn advance for White and the decision to execute a pawn break on c5 for Black are perhaps the most important strategically, although other common structures and ideas are contained in the game.  The tactical threats (some executed, others not) are also important to pay attention to, especially what White could have done with a bishop on h2.

Original ChessBase news article and game commentary by GM Josh Friedel can be found here.

Nemcova, Katerina (2279) - Paikidze, Nazi (2333)

Result: 0-1
Site: Saint Louis
Date: 2015.04.11
[...] 1.e4 c6 2.d4 d5 3.¤d2 this move has little independent value, as Black almost always takes on e4 in response. However, an alternative is ...g6 followed by ...Bg7, in which case White will follow with c3, blunting the pressure on the long diagonal. 3...dxe4 4.¤xe4 ¥f5 the Classical Caro-Kann. 5.¤g3 ¥g6 6.¤h3 an unusual choice. The knight normally goes to f3 and the development N1e2 used to be another popular significant option. The text move is obviously offbeat, but it scores well (58 percent) and has been used in some recent high-level games. 6...¤f6 7.¥c4 (7.¤f4 would transpose to the N1e2 lines.) 7...e6 8.O-O ¥e7
8...¥d6 is often used in the N1e2-f4 lines to fight for the f4 square and is the normal choice here as well. The text move indicates that Black in this game may have had a greater concern for the h4-d8 diagonal and the g5 square. Here's a recent game that parallels White's plan in the main game, using the f4 advance: 9.f4 £c7 10.¢h1 O-O 11.f5 exf5 12.¤xf5 ¤bd7 13.¤xd6 £xd6 14.¥f4 £b4 15.¥b3 a5 16.c3 £b6 17.¥d6 ¦fe8 18.¤f4 ¥e4 19.¤h5 ¥g6 20.¤f4 ¥e4 21.¤h5 ¥g6 22.¤f4 ¥e4 1/2-1/2 (22) Rozentalis,E (2604)-Prohaszka,P (2599) Austria 2015
9.f4 now out of the database, although more because of Black's unusual bishop move. The text move is also usually played in response to ... Bd6 (as shown in the game quoted above). The f-pawn advance is a logical follow-up to Nh3 as an independent line, as White takes advantage of the f4 square being open (i.e. not occupied by a knight). It also influences g5 and e5 to White's advantage. (9.¤f4 is usually where the knight goes.) 9...£d7 this doesn't appear to be a bad move and reinforces f5. However, it blocks the Nb8's development temporarily and the f-pawn's advance is not to be feared. (9...O-O 10.f5 exf5 11.¤xf5 ¥xf5 12.¦xf5 c5) 10.¢h1 this gets the king off the now-weak g1-a7 diagonal and removes future potential tactics involving exchanges on d4 or c5. However, it's also a bit slow and should allow Black to fully equalize.
10.¥e3 played immediately should save a tempo and cover the diagonal.
10...c5!? whenever Black can get this pawn break in effectively without king safety issues, it's normally a good idea. White doesn't appear to have anything useful to do in response. For example, the engine can only come up with 11.f5 exf5 12.dxc5 £xd1 13.¦xd1 O-O
11.¥e3 this reinforces d4 and helps restrain ...c5. However, now that the king is off the diagonal, it's not the most effective use of White's time.
11.¤g5 would seem more to the point here, again logically following up on the presence of the Nh3. Otherwise the knight is effectively doing nothing. Chasing it away with 11...h6?! would simply waste a tempo helping the knight to a better square, from where it could then go to e5 (a much better square).
11...c5 White is now better positioned to combat this pawn break.
11...¤a6 gets the knight into the game and White has nothing better than to exchange it. This shatters the queenside pawn structure, but in Black's favor are the two bishops and a semi-open b-file. 12.¥xa6 bxa6³ Komodo 8 gives Black a small plus here. Black's pieces are, in addition to the above points, better coordinated.
12.f5 White chooses to try for some action on the kingside rather than trade in the center, which would lead to a more simplified position:
12.dxc5 £xd1 13.¦axd1 ¥xc2 14.¦c1 although the engine rates this position as equal, White seems to have the easier position to play, at least for the short term.
12...exf5 13.dxc5 £c8 would preserve the Bg6, unlike the text move. Although the bishop is more of a "big pawn", it does well as a defensive piece on the kingside and is certainly no worse than the Nh3. 14.b4 (14.¤f4 ¥xc5³) 14...¦d8 15.£e2 ¤c6
13.¤xf5 exf5 14.dxc5 ¤g4 Black at this point has achieved equality and just needs to complete her development. The text move is a nice way for Black to threaten the bishop and occupy a rare advanced outpost on the kingside. 15.¥g1 g6 Black should not be afraid to enter into this type of pawn structure when necessary, in this case to protect the advanced f-pawn. The dark square weakness can be covered by the bishop, while White's bishop is in no position to exploit it. 16.¥d5?! this looks overly aggressive. White needs to be careful about the weak c-pawn, which is easily attacked again, and also needs to bring the Nh3 into the game. (16.b4 a5 17.c3) 16...£c7 17.b4 the difference with the earlier variation is that the Qc7 is now pressuring c5 already. Also note the threat to h2 from the knight and queen, which means the Bg1 cannot currently move without allowing a mate. 17...¤c6 Black finally has all her minor pieces developed, and to effective squares. The queen's rook will also go to a nice square on d8.
17...a5!? would more directly attack the exposed queenside. 18.c3 axb4 19.cxb4 ¥f6 20.¦b1 ¤c6 and Black now has the initiative, for example 21.£b3 ¥d4³
18.¦b1 ¦ad8 19.c4 b6 Black has a number of reasonable choices here. (19...¥f6 preparing ...Be5 would redeploy the bishop effectively.) 20.¤f4 White wastes no more time in getting her knight back into the game. 20...bxc5 21.bxc5 The doubled c-pawns may be a long-term weakness, but they're also passed pawns. White's pieces are also now working together much better. 21...¦b8?! Black may have done this just on general principles, without looking at the tactics fully. If she could recapture on b8 with the rook, that would certainly help her position. Unfortunately it doesn't work out that way. (21...¥g5!?)
21...¦c8!? would free the d8 square for the other rook and also line up on the weak pawns.
22.¦xb8 ¤xb8 ugly, but better than the alternative.
22...¦xb8 the main problem with this is that now when the White bishop goes to h2, it has targets on both c7 and b8. 23.h3 ¤ge5 (23...¤f6 24.¥h2 £d7 25.¥xc6 £xc6 26.¤xg6 hxg6 27.¥xb8±) 24.¥h2 ¥f6 25.¤d3 ¦e8 26.£a4±
23.h3²23...¤e5 24.¦e1 White brings her rook to a more effective file and generates additional potential tactical problems for Black, now that the e-file is under pressure. The Qc7 is a bit overloaded, as it cannot protect the Ne5 and support an exchange on c5 at the same time. 24...¥h4 Black's best option, getting the bishop off the e-file and gaining a tempo with the attack on the Re1. 25.¦e2 ¤bc6 26.¥xc6 this dissipates some of White's pressure. The knight will now also get off the e-file. (26.¥h2± still looks very effective.) 26...¤xc6 27.£d6 £c8 Black naturally does not exchange on d6, which would create two monster passed pawns for White. 28.¤d5 this position is probably what White was looking at when she decided to exchange on c6. She still has an edge, but with fewer pieces on the board there are less attacking chances. 28...¦e8 29.¦xe8 £xe8 with the additional exchange, Black probably was looking to head into an endgame with a small disadvantage, but with good drawing chances. The c-pawns look like they can be blockaded effectively. 30.¤c7?! the idea behind this move is not clear to me. In the game, it results in Black's queen moving to a much more effective centralized position, without generating any evident threats.
30.¥f2 would be a clever tactical way to improve White's position and get the Black bishop off the h4-e1 diagonal. The bishop has to protect f6 due to the fork threat from the Nd5.
30...£e4 31.£d5 ¥g3 the bishop is now free to move and attacks the Nc7 "backwards" along the diagonal. 32.¤b5 £e1 with the threat of ...Bf2 33.¤d6? White chooses to counterattack with a threat to f7, but she runs out of threats first, losing the game. (33.¤d4 is the necessary defensive move. 33...¤xd4 34.£xd4) 33...¤e5! holds everything together for Black. 34.£a8 this starts a long sequence where Black's king is chased almost the entire length of the board, but eventually finds refuge.
34.¤xf5 gxf5 35.£d8 ¢g7 36.£g5 ¤g6−⁠+ is the best try for White, but still leaves Black winning. For example 37.£xf5 ¥e5 38.£f2 £c1 39.c6 £xc4 and Black's material advantage is decisive.
34...¢g7 35.¤e8 ¢h6 36.¤f6 ¥f2 Black had to calculate everything precisely to proceed with this move, but saw correctly that White would not be able to deliver mate or get a perpetual check. 37.£f8 ¢g5 38.¤xh7 ¢f4 39.£h6 ¢e4 40.¤g5 ¢d3 White has run out of moves and mate on g1 is coming.
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