This can start with 1...b6, intending 2...Bb7, but more common is 1...d5.
The basic idea is that while White fights for the central dark squares with b4, Bb2, Nf3, etc, Black seeks counter-chances by dominating the central light squares.
The continuation 2.Bb2 Nf6 is very natural, and now White almost always plays 3.e3.
Black can continue the light-square strategy with 3...Bf5, to which White usually replies 4.Nf3 (White's last two moves can easily be reversed, as can Black's).
By continuing 4...e6, Black asks White what is to become of the b4 pawn. There are three replies in ChessBase's 2020 Mega database.
A) 5.c4!?
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| Position after 5.c4!? |
Turkish Team Championship (Konya) 2017
5...Bxb4!?
Blacks have usually declined the pawn, preferring 5...c6, 5...Nbd7, 5...dxc4 or 5...Be7, and their caution has seemed justified as the capture scores poorly in Mega20. But Xu's play in this game seems to turn that assessment on its head.
If you decide 5...Bxb4!? is not for you, then 5...c6 may well transpose into section B) below.
6.Qa4+
My main analysis engines, Stockfish10 and Komodo10, suggest an apparent-novelty, 6.cxd5!? After 6...Qxd5 7.Qa4+ Nc6 8.Bb5, White threatens to win a piece. Black can prevent this with 8...Bd6, whereupon the engines want White to play 9.Bxf6 gxf6 10.Nc3 Qc5 (only move) 11.Nd4. Black should probably castle short, relying on his extra pawn and bishop-pair to offset his theoretically weaker king's position (I write 'theoretically' as White's pieces are not well-placed to attack on the kingside). White can cancel out Black's advantages with 12.Nxf5 Qxf5 13.Bxc6 bxc6 14.Qxc6, but then the engines' 14...Rab8 is at least equal for Black. There are lots of alternatives for both sides along the way, but 6.cxd5!? certainly does not seem a refutation of Black's pawn-grab.
6...Nc6 7.Nd4!
This is better than 7.Ne5, as will become apparent in the game.
7...Rb8!
This is Xu's strong novelty. If White's knight were on e5 rather than d4, he would now be more-or-less obliged to regain his pawn by 8.Nxc6 bxc6 9.Qxc6+. But the engines reckon Black is much better after 9...Nd7! (9...Qd7 is also enough for an edge) thanks to his lead in development. True, White can win a pawn by 10.Bxg7, but after 10...Rg8 11.Bc3 (this seems best) Be7!, Black seems to have more than enough compensation.
8.Nxf5!?
Bogdanovich, not liking the consequences of winning back his pawn, makes the practical choice of giving Black serious kingside weaknesses.
8...exf5 9.cxd5 Qxd5 10.Bxf6 gxf6
Black's extra pawn may not mean much, but his lead in development, and the pressure it gives, is probably why the engines prefer Black.
11.a3 Ba5
Keeping pressure on d2, and discouraging White from playing Nc3.
12.Qc4
If 12.Nc3, then 12...Bxc3 13.dxc3 Ke7! emphasises Black's development advantage.
12...Rd8
This looks very natural, but the engines prefer 12...Qe5!?, when 13.Nc3 f4 suggests White's uncastled king is more vulnerable than Black's.
13.Qxd5 Rxd5 14.Be2 Ke7 15.0-0!
A clever move based on the vulnerability of Black's flank pawns … on the queenside!
15...Bxd2 16.Bf3!
Gaining a tempo over 16.Nxd2 Rxd2 17.Bf3.
16,,,Rd6 17.Nxd2 Rxd2
The game has reached the same position as in the last note, but with White to move rather than Black. That difference is enough to make the position equal, according to the engines, and the game was indeed drawn.
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B) 5.a3
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| Position after 5.a3 |
Jens Ove Fries-Nielsen (2459) - Mads Boe (2341)
Fredricia (Denmark) 2015
5...Nbd7 6.c4
White's main plan in these lines is to chip away at Black's centre.
6...c6
The game actually reached this position by a different move-order (1.e3 d5 2.c4 c6 3.Nf3 Nf6 4.b4 Bf5 5.Bb2 e6 6.a3 Nbd7). Note that, as indicated in section A), this position could also be reached by other move-orders, for example 1.b4 d5 2.Bb2 Nf6 3.e3 Bf5 4.Nf3 e6 5.c4!? c6 6.a3 Nbd7.
7.Be2 dxc4!?
By no means the most-popular move, but an interesting try that is liked by the engines.
8.Bxc4
Practically forced as 8.0-0?! is well-met by 8...a5, and 8.Nc3?! by 8...Bd3 (in both cases, 8...Nb6 also seems good).
8...Nb6 9.Be2
The main result of Black's manoeuvre, starting with ...dxc4, is that he has half-opened the d file with tempo and is already in position to play on that file.
9...Bd3!?
A novelty emphasising Black's play on the light squares.
10.Bxd3 Qxd3 11.Ne5!?
Keeping life in the game. Fries-Nielsen presumably felt 11.Qe2 Qxe2+ was just too drawish for winning chances, even against a player rated more than 100 elo lower.
11...Qd5
Black has a serious alternative in 11...Qa6!?
12.0-0 Nc4!?
Exchanging off White's well-placed knight, but the engines prefer Black to keep the initiative with 12...a5.
13.Nxc4 Qxc4 14.d3 Qh4 15.Nd2 Bd6 16.Nf3 Qh5 17.e4
White has the simple but nasty threat of 18.e5.
17...Bc7
If 17...e5?, then both 18.Nxe5!? and 18.d4!? are strong.
18.Qc2 0-0 19.Rab1 Rac8 20.Bd4 a6 21.Qc3 Rfd8 22.Rb3
22.Bxf6 gxf6 23.Qxf6 Rxd3 is at least equal and may even slightly favour Black.
22...Nd7 23.h3 e5 24.Be3 f6!?
Not just bolstering e5, but also opening a route for the black queen to return to a more-central position. On the downside it weakens Black's kingside light squares, but Boe has judged there is no way for White to exploit this.
25.a4
Fries-Nielsen reckons White's best chance lies in a Minority Attack. He could have tried central play with 25.d4!?, but after, say, 25...exd4 26.Bxd4 Re8 27.Re1 Qf7, the engines conclude Black is fully equal.
25...Bb6 26.Bc5 Qf7 27.Rfb1 Bb7 28.Nd2 Nf8 29.Bxf8!?
Preventing the knight coming to e6, and preparing to pursue his Minority Attack.
29...Kxf8!? 30.b5 cxb5!
Opening the c file for his queen's rook.
31.axb5 Bb6 32.Nc4 Bd4
The engines' 32...a5!? deserves attention.
33.Qd2 Kg8!? 34.bxa6 bxa6 35.Qa2 h6 36.Rb7!?
White can win a pawn with 36.Qxa6, but after 36...Ra8 37.Qc6 (37.Qb7 Qxb7 38.Rxb7 Ra2 is fully equal) Kh7!? 39.Rb7 Qg6, the engines reckon Black's kingside pressure fully compensates for the pawn-minus.
36...Qe6 37.Qe2 Rd7 38.Rb3 Kh7
The game is even, although another 33 moves passed before a draw was agreed.
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C) 5.b5
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| Position after 5.b5 |
US Open 1968
5...a6!?
This is a relatively old game, but I like the way a future grandmaster uses a light-square strategy to make a future California state champion look very ordinary.
It is more normal at this point for Black to develop his dark-square bishop to d6 or e7.
6.a4 axb5 7.axb5
Possible is 7.Bxb5+, but then 7...c6 solidifies Black's position on the central light-squares (often Black feels obliged to play ...c6 in reply to c4, but here he gets the move for free), and he has pressure against the white a pawn.
7...Rxa1 8.Bxa1 Nbd7 9.d4?!
White often plays d4 in the Polish, and in the closely related Nimzo-Larsen (1.b3), when Black has played ...d5, which gives White the possibility of establishing a knight at e5. But here the move, somewhat ironically, weakens White on the dark squares, specifically the d1-a4 diagonal.
Normal is 9.Be2, when 9...Qa8 10.Bb2 h6 (preserving Black's light-square bishop) is equal, according to the engines. Stockfish10's suggestion of 9....h5!?, preserving the light-square bishop and gaining space on the kingside, is also interesting, not least because h5 is a light square!
9...Qa8 10.Bc3
The weakening of the d1-a4 diagonal by 9.d4?! means that here 10.Bb2 is well-answered by 10...Qa2 11.Qc1 (only move) Nb6 12.Nc3 (to stop ...Na4) Qa5 (12...Bb4 is also good) 13.Nd2 (White has to break the pin) Bb4 14.Ncb1, and now probably best is Stockfish10's 14....0-0!? Black is not immediately winning material, but he has such a huge lead in development that it is hard imagining White surviving long.
10...Ne4 11.Bb2?
White had to protect the d1-a4 diagonal by 11.Bd2, after which the engines give 11...Be7 12.Bd3 0-0, much preferring Black.
11...Qa5+
Even stronger seems to be 11...Qa2!?, which is an improved version of the note at move 10 as Black has the added move ...Nf6-e4.
12.Nfd2
The engines reckon this is best. 12.c3?!, for example, runs into 12...Qa2 13.Qc1 Nb6 with massive material-loss to come.
12...Bb4 13.f3
The engines suggest the disgusting-looking 13.Qc1!? Nb6 14.c3 Bd6 15.f3 Nxd2 16.Nxd2, but Black is clearly much better (winning, according to Stockfish10).
13...Nxd2 14.Nxd2 Nb6 15.Qc1
If 15.Be2, then 15...Qa2 forces Qc1 anyway.
15...Na4 16.Ba1 Kd7!?
A bit of a cheeky-looking move, but White is in no position to get at the black king.
17.Kd1
The best the engines can come up with is 17.Bd3!? Bxd3 18.cxd3, but the simple 18...Qxb5 wins a pawn and leaves Black with a strong initiative.
17...Nc3+ 18.Bxc3 Bxc3 19.Nb3 Qb4 20.g4 Bg6 21.h4 h6 22.h5 Bh7 23.Qb1
The engines prefer 23.Bd3!? Bxd3 24.Nc5+ Ke7 25.Nxd3, but after 25...Qd6 Black will follow-up with winning the a file by ...Ra8, generating very strong threats.
23...Ra8 24.Nc5+ Kc8 25.Qxb4 Bxb4 26.Nb3
The exchange of queens has relieved White of the danger of catastrophic loss of material (or mate), but the weakness of his b pawn costs him the game.
26...Ra2 27.Rh2 Rb2 28.Nc1
The only reasonable way to stop 28...Rb1+ 29.Ke2 Bxc2.
28...Rb1 29.Bd3
Black threatened to win a piece with 29...Ba3.
29...Bxd3 30.cxd3 Ba3 31.Rc2 Kb8!?
The most-elegant way to win. Browne has seen that the coming pawn-ending is a simple win for Black. The game finished:
32.e4 Rxc1+ 33.Rxc1 Bxc1 34.Kxc1 Ka7 35.f4 Kb6 36.f5 exf5 37.exf5
Or 37.gxf5 dxe4 38.dxe4 Kxb5 39.e5 Kc6 40.e6 fxe6 41.fxe6 Kd6 42.d5 c6 etc.
37...f6 38.Kb2 Kxb5 39.Kb3 Ka5 40.Ka3 b5 41.Kb3 b4 42.Ka2 Ka4 43.Kb2 b3 44.Ka1 Kb4 45.Kb2 c6 0-1
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