Chess Openings Lab
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French Defense: Diemer-Duhm Gambit

The Diemer-Duhm Gambit is 3.c4, where White ignores the attack on e4 and hits d5 instead. White hopes Black takes on e4 so that lines open, while Black can take the pawn or calmly play ...Nc6 or a bishop check on b4.

Moves
1.e4 e6 2.d4 d5 3.c4
ECO
C00
Engine
−0.80 · a clear edge for Black (Stockfish 17.1, depth 20)
Played
186 games in our lichess sample
White scores
52.4%

Key ideas for both sides

White

  • If Black takes on e4, develop with Nc3 and Be3 and break with f3 to open the f-file.
  • Against 3...Nc6, trading on d5 and playing cxd5 leaves an open game with Bb5 pins on the black knight.
  • Answer a bishop check on b4 with 4.Bd2 and trade bishops, then recapture on e4 with a knight.
  • Keep d4 protected. Without the e-pawn it is White's only central anchor.

Black

  • 3...dxe4 is the engine's choice and the most testing reply, winning a pawn with an easy game.
  • Hold the extra pawn with ...f5 and ...Nf6, as in the top line, and develop the kingside fast.
  • 3...Nc6 hits d4 first and keeps a solid French feel without taking material.
  • 3...Bb4+ trades the dark-squared bishops after Bd2 and leaves Black very comfortable and well developed.

Plans and pawn structure

Everything depends on Black's choice at move three. After 3...dxe4 White plays for activity with Nc3, Be3 and f3, and Black holds e4 with ...f5 or gives it back for development. After 3...Nc6 or 3...Bb4+ the game opens into a quiet position where White's c4 pawn can become a target on an open c-file. White's d4 pawn is the key point in every line.

Where the engine's main line heads: White pawn d4, no e-pawns for White, no d-pawn for Black. White has a pawn on d4 and no e-pawn; Black has no d-pawn. White has more central space; Black's pieces are free and the d4 pawn is a target.

What the engine plays from here

Stockfish 17.1 at depth 20 rates the position −0.80: a clear edge for Black. Its three top choices for Black:

  1. −0.80 3...dxe4 4.Nc3 f5 5.Be3 Nf6 6.Nh3
  2. −0.17 3...Nc6 4.exd5 exd5 5.Nc3 Nf6 6.cxd5
  3. +0.02 3...Bb4+ 4.Bd2 Bxd2+ 5.Nxd2 dxe4 6.Nxe4

Pawns, from White's side.

How it scores on lichess

186 rated lichess games reached this position; White scored 52.4%.

under 120055.7%
1200–159950.0%
1600–199950.0%

Light: White wins. Grey: draws. Dark: Black wins. About the sample.

Where it goes next

How to play against it

As Black, take the pawn with 3...dxe4 and support it with ...f5 and ...Nf6. White has no quick way to regain it and your king castles safely. If you prefer calm play, 3...Bb4+ is also fine: after 4.Bd2 trade bishops and take on e4.

Questions

What are the moves of the French Defense: Diemer-Duhm Gambit?

The French Defense: Diemer-Duhm Gambit starts 1.e4 e6 2.d4 d5 3.c4. Its ECO code is C00.

Is the French Defense: Diemer-Duhm Gambit good for White?

Stockfish 17.1 rates the position −0.80 at depth 20, which is a clear edge for Black. A risky surprise for aggressive White players, since a prepared Black player either keeps a pawn or equalizes easily.

What is the main idea of the French Defense: Diemer-Duhm Gambit?

White gambits the e4 pawn with 3.c4 to open lines and race ahead in development. Black has several good answers, and taking the pawn with 3...dxe4 is the strongest.

What should Black play next?

The engine's first choice is dxe4, with Nc6 and Bb4+ close behind. 3...dxe4 grabs a central pawn that White cannot easily win back, and ...f5 can hold it.

Updated October 2026. Sources and method.