Blackmar-Diemer Gambit

The Blackmar-Diemer Gambit begins when White plays d4 and then e4 against a black pawn on d5. A gambit is a voluntary material offer, usually a pawn, in return for activity, development time, or open lines. If Black accepts on e4, White commonly develops Nc3 and plays f3 to attack that pawn.

If Black also captures the f3-pawn, White can recapture with a piece and obtain a half-open f-file, a file on which White no longer has a pawn while Black still does. That line can help a rook pressure the kingside. White's compensation, the activity gained in return for the sacrificed pawn, depends on bringing pieces out quickly and creating threats before Black's extra pawn becomes important.

The opening is not a forced win. Accurate defense can return the pawn at a convenient moment or consolidate the material advantage. It is therefore more useful to understand the initiative, meaning the ability to make threats that force replies, than to rely only on traps.

The Blackmar-Diemer trades a pawn for tempi and lines

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Starte4dxe4Nc3Nf6f3exf3Nxf3

e4 is the gambit offer: White permits a capture in order to accelerate piece activity.

White offers a second central pawn

e4 challenges d5 and lets Black accept material at the cost of development tempi.

1. e4 is the gambit offer: White permits a capture in order to accelerate piece activity.