London System [D00 & D02]
Still, already more interesting than the 7...g6 (with the same idea of bringing the bishop onto the b1-h7 'London' diagonal, but allowing 8.e4! with enhanced effect) I examined in March, there is a possibility this bind may become effective if White is not cautious after 1.d4 d5 2.Bf4 Nf6 3.e3 c5 4.c3 Nc6 5.Nd2 Qb6 6.Qb3 c4 7.Qc2 Bg4!?:
Thus Black brings his light-squared bishop outside the pawn chain, planning to defend d5 with a pawn on e6 in case of the further advance e3-e4, and with the probable intention ...Bh5-g6.
Game One continued 8.Be2 Bxe2 9.Nxe2 e6 10.0-0 Be7 11.Ng3! (Thus preserving the strong London bishop.) 11...0-0 12.e4 with a white edge since Black would like to counter-attack on the queenside but without the privileged possession of the b-file (because of the bishop on f4), its opening after ...b5-b4xc3 will likely only result in weakening his own c4-pawn.
9...Bh5! 10.Bxh5 Nxh5 is the problem, however:
when White had to part with his London bishop in Game Two and, after the unavoidable advance e3-e4, mount a much more complicated attack than in the previous game.
The move b2-b3 is the key to break the bind and offer White good play, although it gave White some cold sweat in Game Three after the loss of time 8.Nf3 e6 9.b3 Bf5, forcing the white queen to lose a tempo passing by c1 (10.Qc1) in order to force the capture c4xb3 since the b3 pawn would be pinned if (as in Prie-Perez Candelario...) she stood on b2.
If Black has already committed his king pawn to e6 during the very first moves of the game, but hasn't played ...c5, then proposing the exchange ...Bd6 vs Bf4 (which had been denied to Black in my game against Svetushkin because of the Nimzo move order of ...c7-c5 before ...d7-d5 in last month's astonishing Novelty) faces both players with another set of subtle problems. For instance, Black may then recapture on d6 with his c-pawn, and this is the main objection to the idea of the previous update of keeping White's king's knight back. On the other hand, now White may also use his c-pawn in a more enterprising way by going forward 2 squares rather than just defend his central d-pawn, especially if his queen's knight can still develop to the c3-square.
This is the option White chose in Game Four after 3...e6 4.Nf3 Bd6 5.Bxd6!? cxd6 6.c4 0-0 7.Nc3 dxc4 8.Bxc4 b6 9.0-0 Bb7 10.Qe2:
demonstrating that with a slightly better bishop, a little more space and some extra time, these symmetrical positions can be treacherous for the second player.
Keeping the status-quo with e2-e3, hoping to form a bind on the e5 square after the exchange of the dark-squared bishops on f4 in the Bd6 vs Bf4 configuration, represents another playable option for White. This is approximately what he obtained in Game 5 with a good square for a knight on d4 but not really enough to unbalance the position because of the lack of flexibility of his altered structure.
When Black refrains from playing ...c5 before offering the exchange on d6 then the interception Nf3-e5 prevents him from playing this indispensable complement to the black set-up before castling. As Black learnt to his cost in Game 6.
All this, especially in the light of the previous update, means that the most promising course of action for White (except when his h-pawn has already moved!), whatever the order of moves, consists of the retreat of the London bishop to g3 when offered the exchange. Then 4.Nd2 is probably a bit more precise than the 4.Nf3 of game 4. The reason is that after 4...Bd6 5.Bg3 0-0 6.Bd3! b6 7.Qe2 it is not so easy for Black to realize the pending exchange of the light-squared bishops this time, making the best enemy asset in the attack disappear.
Black followed another idea in Game 7, anyway, keeping his bishop on b7...
Going back to Game 1's order of moves, 6.Qb3, although dubious, is what Black is regularly afraid of when playing the correct 5...Bf5! Then we have known the antidote 6...Qd7! with the idea ...c5-c4 for a long time, here on ChessPublishing, but 6...Na5!? 7.Qa4+ Bd7 8.Qc2:
as in Game 8, may also prove satisfactory.
See you soon, Eric