The Blackmar–Diemer Gambit (or BDG) is a chess opening characterized by the moves:
1. d4 d5 2. e4 dxe4 3. Nc3
White intends to follow up with f3, usually on the fourth move. White obtains a tempo and a half-open f-file in return for a pawn, and as with most gambits, White aims to achieve rapid and active posting of their pieces in order to rapidly build up an attack at the cost of the gambit pawn. It is one of the few gambits available to White after 1.d4.Blackmar–Diemer Gambit, Chess Digest (1977), p.5. The gambit can also be reached from the Scandinavian Defense (1.e4 d5) if White plays 2.d4.
History The Blackmar–Diemer Gambit arose as a development of the earlier Blackmar Gambit, named after Armand Blackmar, a relatively little-known New Orleans player of the late 19th century who popularized its characteristic moves (1.d4 d5 2.e4 dxe4 3.f3) and was the first player to publish analysis of the opening.Armand Edward Blackmar at Chessgames.com.
The popularity of the original Blackmar Gambit, however, was short lived, as it was basically unsound, allowing Black to secure a superior position after White's immediate 3.f3 with 3...e5. In 1889, Ignatz von Popiel came up with the idea of 3.Nc3, although his main idea was to meet 3...Nf6 with 4.Bg5 (rather than the more usual 4.f3). He also provided analysis of the Lemberger Countergambit (3.Nc3 e5), which was common at the time.
The evolved, modern form of this gambit owes much to the German master Emil Josef Diemer (1908–1990), who popularized the continuation 3.Nc3 Nf6 and then 4.f3 (when 4...e5 is ineffective as 5.dxe5 hits Black's knight, and after 5...Qxd1+ 6.Kxd1 the knight has to retreat to d7 or g8). The position resulting after 3... Nf6 4.f3 reflects the main line of the gambit accepted, although other Black responses on move three are possible. After many years of analysis, Diemer wrote a book on the opening in the late 1950s, titled Vom Ersten Zug An Auf Matt! (Toward Mate From The First Move!), with most of the published analysis devoted to the Ryder Gambit (and associated Halosar Trap), a double-pawn sacrifice characterized by the moves 4...exf3 5.Qxf3.
Assessment This gambit is considered an aggressive opening, but its soundness continues to be the subject of much debate both on and off the chessboard. Dismissed by many masters on the one hand, and embraced enthusiastically by many amateurs on the other, many consider that Black has good chances of defending successfully and converting the extra pawn in the endgame, while theory suggests that Black has many ways to . As a result, this opening is almost never seen in top-level play, but enjoys a certain popularity among club players. Some titled players, including International Master Gary Lane, consider the opening to be suitable at the club level and for young and improving players. In one of his Keybooks, the Rev Tim Sawyer said, "Stop playing for the endgame, play to end the game! Be a winner. Play the Blackmar–Diemer Gambit!"Scheerer 2011, p. 9. On the other hand, Sam Collins (in his book Understanding the Chess Openings) noted the tendency for some Blackmar–Diemer fanatics to try to get the opening in every game, thus limiting their chess experience, and concluded, "Nobody who plays good chess plays this line, and nobody who plays good chess ever will." Other dismissive quotes include "playing the Blackmar–Diemer Gambit is like shopping for a tombstone" (Andrew Martin) and "To convince an adherent of the BDG that it is unsound, is like trying to convince a child that there is no Santa Claus." (Kevin Denny). As a result of the intense controversy surrounding the opening, much of the literature on the opening is lacking in objectivity.Scheerer 2011, p. 10
GM Boris Avrukh has written that the gambit "may not be fully correct" but cautioned that he "was surprised at just how potent White's initiative could become". Although he was unable to fully refute the gambit and considered that Black faced a non-trivial defensive task, he felt that with correct play Black could emerge with good chances. GM Joe Gallagher wrote that he had "noticed a common trend among Blackmar–Diemer analysts; once there is no attack and the position looks rather balanced they tend to assess the game as =, forgetting the fact that they are a pawn down." Gallagher thought that the closely related Hübsch Gambit gave an equal game but that the Blackmar–Diemer provided "not really enough compensation" and there were "a number of areas where Black could fight for the advantage." Nevertheless, he cautioned that Black "inaccuracies can be swiftly punished" in the Blackmar–Diemer. IM John Cox wrote that the gambit was "objectively weak" but pragmatically recommended that Black should enter the Hübsch gambit instead of accepting the Blackmar–Diemer as "sod's law dictates that [the reader would meet the gambit] in the third Saturday game of a weekender, when few of us are at our sharpest tactically ... one slip sees you getting torched." IM Willy Hendriks notes that the main lines of the Blackmar–Diemer (1.d4 d5 2.e4 dxe4 3.Nc3 Nf6 4.f3 exf3 5.Nxf3) and the King's Gambit (1.e4 e5 2.f4 exf4 3.Nf3) have the same engine evaluation, and philosophically wonders whether the two might have swapped places in an alternative history.
Main line: 3...Nf6 4.f3 exf3 5.Nxf3
After 1.d4 d5 2.e4 dxe4 3.Nc3 Nf6 4.f3 exf3 5.Nxf3, Black has five main options: 5...Bf5, 5...Bg4, 5...e6, 5...g6, and 5...c6.
Gunderam Defence: 5...Bf5 The line 5...Bf5 (along with most of the ...c6/...Bf5 defences for Black in general) was extensively analysed by Gerhart Gunderam, who published his analysis in a book Blackmar–Diemer Gambit in 1984.Scheerer 2011, p. 206. The main response for White is 6.Ne5, intending to attack the black bishop with an advance of the kingside pawns and, if appropriate, weaken Black's kingside pawn structure with Ne5xBg6. Black can respond with 6...e6, when after 7.g4, 7...Be4 leads to tremendous complications, e.g. after 8.Nxe4 Nxe4 9.Qf3 Qxd4 10.Qxf7+ Kd8 11.Qf4.Scheerer 2011, p. 216 More common is 7...Bg6, which leads to quieter play, when White's best response is probably 8.Bg2 c6 9.h4, with a sustained kingside initiative in return for the pawn.Scheerer 2011, p. 218 However, Black also has the option 6...c6 intending 7.g4 Be6, when White has to play accurately to prove enough compensation for the pawn after 8.g5 Nd5 or 8.Bc4 Nd5 9.Qe2 Nd7.Scheerer 2011, p. 219. White has an alternative in 6.Bd3, directly challenging the bishop, but Christoph Scheerer doubts that White gets enough compensation after 6...Bxd3 7.Qxd3 c6 intending ...e6, ...Nbd7, ...Be7 and ...0-0 with a solid position.Scheerer 2011, p. 207
Teichmann Defence: 5...Bg4 The move 5...Bg4 pins the knight on f3, often with the intention of swapping it off and undermining White's central control.Scheerer 2011, p. 233. White's best response is to attack the bishop immediately with 6.h3, when play often continues 6...Bxf3 7.Qxf3 c6 (but not 7...Nc6, when 8.Bb5 is good for White). In this position, White can defend the attacked d-pawn with 8.Qf2 (the Ciesielski Variation), but this allows Black an easy game by preparing ...e7–e5, e.g. after 8...Nbd7 9.Bd3 e5.Scheerer 2011, p. 258 Alternatively, 8.Be3 is the Classical Variation, where White aims for a slow buildup to a kingside offensive. White's other main alternative is 8.g4, the Seidel–Hall Attack, where White is happy to sacrifice the d-pawn in order to gain an increased initiative on the kingside, e.g. after 8...Qxd4 9.Be3 Qe5 10.0-0-0 e6 11.g5. Black can decline the pawn, e.g. after 8...e6 9.g5 Nd5 10.Bd3, leading to sharp play.Scheerer 2011, p. 262. Alternatively, after 6.h3, Black can retreat the bishop with 6...Bh5 7.g4 Bg6 8.Ne5, a line which often transposes to the Gunderam Defence line 5...Bf5 6.Ne5 e6 7.g4 Bg6 after a subsequent h3–h4, as White's extra tempo with h3 is not particularly useful.Scheerer 2011, p. 234
Euwe Defence: 5...e6 The 5...e6 line, analysed by Max Euwe, aims to reach a French Defence type position, but with Black having an extra pawn. Play usually continues 6.Bg5 Be7, when White's most popular option is 7.Bd3. Black can attack the centre immediately with 7...c5!? here, as recommended by Joe Gallagher and James Rizzitano.Scheerer 2011, p. 145 Play can continue 8.dxc5 Qa5 9.0-0 Qxc5+ 10.Kh1, when White has to play accurately to prove compensation for the pawn. Alternatively 7...Nc6 can be considered the main line of this variation, when 8.0-0 Nxd4 9.Kh1 is the notorious Zilbermints Gambit, sacrificing a second pawn in order to increase White's initiative. The Zilbermints Gambit has scored well in practice, but objectively it probably does not give White enough compensation for two pawns. However, the alternative 8.a3, despite the loss of time, offers White good compensation for the pawn, and White can also consider 8.Qd2, allowing the trade of the bishop on d3 but avoiding any loss of time.Scheerer 2011, p. 155. White's main alternative to 7.Bd3 is 7.Qd2, aiming to castle queenside and giving additional support to the d4-pawn, while aiming to launch a kingside offensive with Qd2–f4 and meeting ...h6 with a dangerous Bxh6 sacrifice. Play can continue 7...0-0 8.0-0-0 (8.Bd3 c5! is better for Black) 8...c5 9.Qf4!? cxd4 10.Rxd4Scheerer 2011, p. 163 or 7...h6 8.Bh4 (8.Bf4 is also possible, aiming to keep the Bxh6 sacrifice possibility open, but allowing 8...Bb4 9.Bc4 Ne4)Scheerer 2011, p. 167 8...Ne4 9.Nxe4 Bxh4+ 10.g3 Be7 11.Bg2, when White has some compensation for the pawn but the final verdict on the resulting positions is still yet to be reached.
Bogoljubov Defence: 5...g6 The Bogoljubov Defence was played by Diemer himself in a game against Bogoljubov. By fianchettoing the king's bishop Black aims to gain increased pressure against the d4-pawn following a subsequent ...c5. White's most common response is the Studier Attack, 6.Bc4 Bg7 7.0-0 0-0 8.Qe1, intending Qh4, Bh6 and piling pressure on the kingside, sacrificing pawns at d4 and c2 if appropriate. However, after Peter Leisebein's 8...Nc6 9.Qh4 Bg4!, it is doubtful if White obtains enough compensation for the pawn against accurate play.Scheerer 2011, p. 200 An alternative approach is to castle queenside, play Bh6 and then launch the h-pawn against the black kingside. The best way to carry out this approach is via 6.Bf4, as 6.Bg5 (as played by Bogoljubov in his game against Diemer) is well met by 6...Bg7 7.Qd2 0-0 8.0-0-0 c5!, when Black stands better.Scheerer 2011, p. 170 If Black tries the same approach against 6.Bf4, i.e. 6...Bg7 7.Qd2 8.0-0-0 c5, then 9.d5 a6 10.d6! gives White good chances.Scheerer 2011, p. 204
Ziegler Defence: 5...c6