Beat The ... Blackmar-Diemer Gambit

IN this series I am looking at the statistically best way to play against popular opening lines.

The numbers are drawn from the 2021 edition of ChessBase's Mega database, ignoring, where possible, those results that include very few games and so are statistically insignificant.

The Blackmar-Diemer Gambit arises from two move-orders: 1.d4 d5 2.e4 and 1.e4 d5 2.d4.

Black can immediately decline the gambit with 2...e6, which scores 42%, and with 2...c6, which scores 46%, but 2...dxe4 easily beats these moves by scoring 50%.

After 3.Nc3, Black's usual response is 3...Nf6, which scores 50%, but 3...e5!? boosts Black's score to an excellent 55%.

Position after 3...e5!?

White has five replies that occur with any degree of frequency.

A) 4.Nxe4 (76 games)

We are already dealing with small numbers of games, but Black's commonest move, 4...dxe4 scores 47%, while 4...Nf6 and 4...Nc6 score 50%. Both knight moves are uncommon, but I have gone with ...Nc6 as it is the rarer of the two and is much preferred by the analysis engines Stockfish13 and Komodo12.1.1.

Just four games have reached the position after 4...Nc6 in Mega21, so below is what the engines view as best play from the three moves that have been played by White.

A1 5.Nf3 exd4 6.Bb5 Bf5 6.Bxc6+ bxc6 7.Ng3 Qe7+ 8.Ne2, when the engines reckon the position is dead-equal after 8...0-0-0 and after 8...Be4.

A2 5.Bb5?! Qxd4 6.Qxd4 exd4 7.Nf3 Bf5 8.Bxc6+ bxc6 9.Ng3 Bxc2 10.Nxd4 Bb4+ 11.Bd2 Bxd2+ 12.Kxd2 0-0-0, when both engines give Black a slight edge.

A3 5.d5 Nb4 6.Bb5+ c6 7.dxc6 bxc6!? 8.Ba4!? Bf5 9.Ng3 Qa5!? 10.Bxc6+ Nxc6 11.Bd2 Bxc2 12.Qxc2 Qa6, when Komodo12.1.1 gives Black a slight edge but Stockfish13 reckons Black's advantage is minimal (+.18).

B) 4.dxe5 (74 games)

After 4...Qxd1+, the line splits.

B1 5.Kxd1 Nc6, when B1.1 6.Nxe4 Bf5!? 7.Ng3 0-0-0+ scores 75% for Black, albeit from a very small sample, and B1.2 6.Bb5 Bd7 scores 100% for Black, albeit from a very small sample.

B2 5.Nxd1 Nc6, when B2.1 6.Bb5 Bd7 scores 69% for Black, albeit from a small sample, and B2.2 6.Bf4 Nge7 7.Bb5 Bd7 8.Nc3 Ng6 scores 100% for Black, albeit from a very small sample.

C) 4.Qh5 (62 games)

After 4...exd4!? 5.Bc4!? Qe7 Black scores 69%, albeit from a small sample.

D) 4.Be3 (43 games)

After 4...exd4 the line splits.

D1 5.Bxd4 Nc6 6.Bb5 Bd7 scores 73% for Black, albeit from a small sample.

D2 5.Qxd4 Qxd4 6.Bxd4 Nc6 scores 50% for Black, albeit from a very small sample.

E) 4.d5 (32 games)

The move 4...f5!?, which has been played by Swedish grandmaster Jonny Hector, features just twice in Mega21, but both games were won by Black and the move is liked by the engines.