DDG 4.Nc3 Bb4

Most lines after 4...Bb4 transpose to the 4...Nf6 5.f3 Bb4 variation, so here are only considered lines where Nf6 is deferred. White often tends to castle queenside in these lines.

W	5.Qa4+! 5.Qb3! 5.Be3 5.Ne2 5.f3?! 5.Bd2?! 5.Various

5.Qa4+!

5.Qa4+! used to be considered the best. The chief idea is to prevent Black from playing c5; sometimes White also intends to castle queenside. It is useful to study how this differs from 6.Qa4+ in the Kmoch Variation, where f3 and Nf6 have been played.

5...Nc6

6.Be3 Bd7
- 7.Qc2 f5 (with advantage to Black [ECO]; 7...Nf6 transposes) 8.O-O-O!? Nf6 9.f3 [Minev].
- 7.Qd1 f5 8.f3 g5 9.fxe4 f4 10.Qh5+ Kf8 11.d5 Qf6 12.Bd2 exd5 13.cxd5 Nd4 14.Bd3 Nh6 15.Nf3 Bg4 0-1, Sperling - Diemer, 1955.
- 7.O-O-O Bxc3 8.bxc3 Nxd4! with advantage to Black [Schwarz].
- 7.d5?! exd5 8.cxd5 Nd4 9.Qd1 Qe7 and Black has the initiative.
6.Bd2 Bd7! 7.O-O-O?! (7.Nxe4 Nxd4! with advantage to Black [Schwarz]) Bxc3 8.Bxc3 Nxd4 9.Rxd4 Bxa4? 10.Rxd8+ Rxd8 11.b3 +/-, but Black has simple 9...Qg5+ 10.Bd2 Qxd2+ 11.Kxd2 Bxa4 12.Rxe4 -/+. In practice, 6...Qxd4 has been played:
- 7.a3 Bc5 8.O-O-O Bd7 9.Nge2 Qe5 10.Bf4 Qf5 11.g4 Qg6, 1-0 in 31, Bode - Menke .
- 7.O-O-O! Qxf2 (7...Bxc3 8.Bg5 Bxb2+ 9.Kb1 Qb6 10.Rd8# 1-0, Diemer - Buerger, 1948) 8.Nh3 (8.a3 e3 9.Be1 Qxf1 10.Bh4 Qxd1+ =/+, Heikkinen - Rebel Decade, 1995) Qf5 9.Be2 Qa5 10.Qc2 Bxc3 11.Bxc3 Nb4 12.Qd2 Nxa2+ 13.Kc2 Qa4+ 14.b3 Nb4+ 15.Bxb4 Qa2+, 0-1 in 25, Heikkinen - Rebel Decade, 1995.
6.d5? exd5 7.cxd5 Qxd5 8.Bb5 Bd7! with advantage to Black [Schwarz].
6.a3 Bxc3+ 7.bxc3 Nf6 8.f3 transposes to the Modern Main Line.

5.Qb3!

5.Qb3 is now my favorite.

A) 5...c5 6.a3!!

6...Bxc3+ 7.bxc3 cxd4 8.cxd4 Qxd4? 9.Bb2 [Diemer].
6...cxd4 7.axb4 dxc3 8.bxc3 Qf6 9.f3? Nh6 10.h4 Qg6 11.Bf4 Nd7 12.O-O-O e5 13.Bd2 a5 14.fxe4 (14.h5) axb4 15.cxb4 Qxe4, 1-0 in 35, Heikkinen - Siikonen, 2002, even though White deserved to lose after the lousy opening.

B) 5...Nc6 6.Be3 Nf6 (6...f5 transposes) 7.O-O-O! [Diemer]

7...Qe7 8.Nb1 Na5 9.Qc2 c5 10.a3 cxd4 11.axb4 Qxb4 12.Rxd4 Nb3+ 13.Kd1 Nxd4 14.Bxd4 1-0, Diemer - Werner, 1950.
7...Bxc3 8.Qxc3 Qe7 9.f3 Nb4 10.Kb1 a5 11.a3 Na6 12.Qc2 exf3 13.Nxf3 Bd7 14.Bd3 c6 15.Bg5 h6 16.Bh4 Nc7 17.Rhf1 b5 18.Ne5 bxc4 19.Bxc4 Ncd5 20.Bxd5 cxd5 21.Ng4, 1-0 in 33, Heikkinen - Paasonen, 2001.
7...O-O? 8.d5 Bxc3 9.dxc6 Bxb2+ 10.Qxb2 Qe7 11.Ne2 (11.cxb7!?) bxc6 12.Nd4 Bd7 13.Nb3 Rfb8 14.Bc5, Heikkinen - Eriksson, 2002.

7.a3 Ba5 8.Rd1 Ng4 9.Bf4?! Nxd4 10.Qa4+ c6 11.b4 e5! 12.Be3 Bb6 13.c5 Bc7 14.h4 -/+, Heikkinen - Rebel Decade, 1996.

7.f3 transposes.

C) 5...Ba5 6.Be3 Ne7 7.O-O-O Bxc3 8.Qxc3 Nf5 9.Bf4 f6?! 10.h4 b6 11.f3 exf3 12.Qxf3 c6 13.Bd3!? Ne7? 14.Qg3 Na6 15.Qxg7 Rg8 16.Qxh7 Bb7 (16...Rxg2?? 17.Be4) 17.d5! cxd5 18.cxd5 Rc8+ 19.Kb1 Nc7 20.dxe6 a6 21.Qf7# 1-0, Heikkinen - Nylund, 2001.

5.Be3

I have learned to like the Be3 move in the DDG: it looks good in almost any variation. Here, for instance, it allows White to continue with Qc2 and Rd1 -- or even O-O-O!?.

5.Be3 Bxc3+

5...c5 6.Qd2 Nf6 7.dxc5 Qxd2+ 8.Kxd2 Ng4 9.a3 Bxc3+ 10.Kxc3 Nxe3 11.fxe3 a5 12.Be2 Nd7 13.Kd4 f5 14.Nh3 a4 15.g4 Ra5 16.Rhg1 Nxc5 17.Kc3 O-O 18.Rad1 draw, Jorgensen - Heikkinen, corr. 2000.

6.bxc3 Nf6

6...f5 7.Qh5+ g6 8.Qd1 Nc6 9.h4 Qe7 10.Bg5 Nf6 11.h5 O-O 12.hxg6 hxg6 13.a4 Rf7 14.Rh6 Kg7 15.Ne2 e5 16.Qd2 Bd7 17.Ng3 f4 18.dxe5 Nxe5 19.Bxf4 Nfg4 20.Rh1 e3 21.Qd4 exf2+ 22.Ke2 Rxf4 23.Qxf4 Rf8 24.Qe4 Bc6 0-1, Heikkinen - Fuller, corr. 1997.
6...c5! 7.Qc2 Qa5 8.Bd2 Nf6 9.f3 e3!? 10.Bxe3 cxd4 11.Bxd4 Nbd7 +/=, or 8...f5 =/+.

7.Qc2 (7.f3 c5 8.Qa4+ Bd7 9.Qb3 Bc6 =/+)

7...b6 8.f3 Bb7 9.fxe4!? Bxe4 10.Bd3 Bxd3 11.Qxd3 c5 12.Bg5 with the idea Bxf6 and Qe4.
7...Bd7 8.f3 exf3 9.Nxf3 Nc6 10.Bd3 h6 11.O-O O-O 12.Rb1 Qc8 13.h3 Rd8 14.Nh4 e5, 1-0 in 24, Strange - Robinson, 1995.

5.Ne2

5.Ne2 is interesting. White does not attack the pawn on e4 straight, and may even castle queenside.

5...Nc6

6.Be3 Nge7 7.Qc2 f5 8.a3 Bxc3+ 9.Qxc3 O-O 10.b4 Ng6 11.b5 Nce7 12.g3 a6 13.bxa6 Rxa6 14.h4 Rc6 15.h5 Nd5 16.Qb3 Nxe3 17.hxg6 Ng4 18.gxh7+, 0-1 in 41, analysed Rebel Decade, 1996 !.
6.Bf4 Nf6 7.a3 Bxc3+ 8.bxc3 Nh5 9.Be3 O-O 10.Ng3 Nxg3 11.hxg3 h6 12.Qh5 Qe7 13.Bxh6 gxh6 14.Qxh6 f5 15.Qh8+ draw, Laucius - Genius 5, 1997.

5...c5 6.d5 Nf6 7.a3 Bxc3+ (7...Ba5 8.b4!) 8.Nxc3 exd5 9.cxd5 Bg4 with interesting game.

5.f3?!

5...c6 6.Qb3 Bxc3+ 7.Qxc3 Nf6 8.Bg5 exf3 9.Nxf3 O-O 10.Bd3 Nbd7 11.O-O b6 12.Ne5 Qc7 13.Bxf6 Nxf6 14.Rae1 Bb7 15.Rxf6 gxf6 16.Bxh7+ Kxh7 17.Qh3+ Kg7 18.Qg3+ Kh7 19.Re4 1-0, Ruth - Ramsey, 1908.
5...c5!
- 6.d5 exf3 (6...Nf6 7.d6!? exf3 8.gxf3 Nh5 9.h4 Ng3 10.Rh2 Nf5 11.Bf4 -/+, or 8.Nxf3 Ne4) 7.Nxf3 Nf6 8.Bg5 h6 9.Bxf6 Qxf6, 0-1 in 25, Heikkinen - Rebel Decade, 1995.
- 6.dxc5 Qxd1+ 7.Kxd1 Bxc3 8.bxc3 exf3 9.Nxf3 f6, 0-1 in 32, Heikkinen - Pietarinen, corr. 1994.
- 6.Be3 exf3 7.Nxf3 cxd4 8.Bxd4 Nf6 9.a3 Ba5 10.b4 Bc7 11.Nb5 Na6 12.Nxc7+ Nxc7 13.Be2 b6 14.c5 Ncd5 15.Bb5+ Bd7 16.c6 O-O 17.cxd7 Nxd7 18.Qa4 N7f6 19.Bc6 Rc8 20.b5 Ne7 21.Bxf6 gxf6 22.Rd1 Qc7 23.Rd7 Nxc6 24.Rxc7 Rxc7 25.bxc6 1-0, Brause - dostoevsky, FICS 1996.
5...Nf6, 5...exf3 and 5...Bxc3+ transpose.
5...Nc6 6.d5 Ne5?? 7.Qa4+ +- is a cheap trick, but has worked well in several blitz games.

5.Bd2?!

5.Bd2?! offers another pawn for almost nothing. White sacrifices a pawn in the DDG in order to get the half-open e-file (and possibly f-file), as well as the open diagonal b1-h7, but I have not figured out what is the idea of sacrifing this second pawn. After that, Black's plan looks too obvious: exchange pieces, and win an easy endgame. However, even Brause has played this double-sacrifice.

5...Qxd4 6.Qb3 Nc6 7.Nge2 Qe5 8.Rd1 Nf6 9.Nxe4 Bxd2+ 10.Nxd2 O-O 11.Qc3 Qxc3 12.Nxc3 Nb4, 0-1 in 66, Brause - Vampire, FICS 1996.

5...f5? seems to be losing a piece for nothing.

6.Qa4+ Nc6 7.d5 exd5 (7...Bc5 was suggested by Genius 2, but White's advantage is decisive in any case) 8.cxd5 e3 (8...Bxc3 9.Bxc3 Qxd5 10.Bxg7 +/-) 9.fxe3 Nge7 10.dxc6 Nxc6 11.Bb5 Bxc3 12.Bxc3 O-O 13.Nf3 Qe7 14.Qf4 a5 15.O-O Kh8 16.Qh6 1-0, corr. Cromsigt - Washburn, 1996. 16...f4 would have set a nice trap: 17.e4? (intending Ng5 and preventing Bf5) Qc5+ 18.Kh1 Qxc3! =.
6.Nge2 Bd7 7.Nxe4 Bxd2+ 8.Nxd2 Nf6 9.Qb3 Bc6 10.Qe3 Qe7 11.Nf4 Ne4 12.Bd3 O-O 13.d5 exd5 14.cxd5 Bd7 15.Bc4 Kh8 16.Ng6+ hxg6 17.Qh3+ Kg8 18.d6+ 1-0, Brause - killerbie, FICS 1996.

Various

5.a3 Bxc3+ 6.bxc3 Nf6 7.Rb1 (7.f3 transposes) O-O 8.Be2 b6 9.Bf4 c6 10.Nh3 Qe7 11.Qa4 Nfd7 12.O-O Ba6 13.Bxb8? -+ Nxb8 14.Rfd1 f5 15.Kh1 e5 16.dxe5 Qxe5, 0-1 in 49, Wita - Tyro, 1977. This game was played in the North American Computer Chess Championship, and has been published without comments in several computer chess books, thus being most likely the most quoted DDG game. Who said computers cannot sacrifice?
5.d5?! c6 and Black has very good game. Of course, 5...Nf6?? 6.Qa4+ wins a piece.