Ideas Behind the DDG

B	"All openings are sound below master level." (Lombardy) "Like the BDG, it is widely condemned. Still, ..." (Tom Purser)

In Spanisch bis Französisch (1974), Paul Keres mentions bizarre systems against the French Defence. In addition to 3. Be3, he gives the following line (translation from German). IM John Watson agreed with Keres in his brief analysis.

"3. c4 (this pawn sacrifice is not correct) dxe4 4. Nc3 Nf6 (possible are also 4... Bb4 and 4... f5) 5. f3 c5 6. d5 exd5 7. cxd5 exf3 8. Nxf3 Bd6, and Black has good position with a healthy pawn."

Chessmaster 3000 gives the following English Language Analysis:

1. The Chessmaster recommends: Pawn takes pawn on e4.
2. Analysis: Your pawn captures pawn on e4. White responds by moving the knight to c3, which threatens your pawn on e4. You move your knight to c6. White responds by moving the knight on g1 to e2.
3. As a result of this line play, you win a pawn. In addition, your attack potential is somewhat increased. Also, the development of White's pawns is somewhat weakened.

In my view, 3. c4 is based on these ideas:

1. White can ruin Black's plan to play a semi-closed game: one in which the center files generally remain closed, thus enabling Black to build up a solid position in the center.
2. White can play Bc2 and Qd3 to attack h7, which has been proved lethal if Black dares castle kingside. The c4 move makes the DDG different from the BDG, where White often plays Bd3 and Qe1-h4. In the BDG, White can also safely castle queenside.
3. Black is prevented from playing Nd5, which is typical in the Alapin French, where White has played Be3. If Black plays c5, White can advance to d5, thanks to c4. White can also give a check with Qa4 if Black plays Bb4.
4. White plays f3 to get the half-open f-file, and after castling kingside, the rook is ready to attack. If Black does not play exf3, White can play fxe4, either regaining the pawn, or winning a tempo after Nxe4, Qd3, Nf6.
5. If Black plays Bb4, White usually gets the bishop pair. Bg5 is often decisive in pinning Nf6 (DDG à la pin).
6. The tendency to create sharp attacks is a way to avoid long endgames. The name of Diemer's book that introduced the DDG crystallizes it: Towards Mate from the First Move.