Chess Openings Lab
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French Defense: Diemer-Duhm Gambit Accepted

The Diemer-Duhm Gambit Accepted arises after 3.c4 dxe4, when Black takes the offered e4 pawn. White hopes for open lines and quick development, while Black holds the extra pawn with ...f5 or attacks d4 with ...Nf5.

Moves
1.e4 e6 2.d4 d5 3.c4 dxe4
ECO
C00
Engine
−0.77 · a clear edge for Black (Stockfish 17.1, depth 20)
Played
350 games in our lichess sample
White scores
46.4%

Key ideas for both sides

White

  • Develop with Be3 and Nc3 to protect d4 and prepare a recapture on e4.
  • Play f3 to open the f-file and get piece play, as the second engine line shows with Qd2 next.
  • The queen on b3 can hit b7 if Black is slow to develop the queenside pieces.
  • Expect to stay a pawn down or regain it only after losing time. This is a gamble, not a sound pawn sac.

Black

  • Defend the e4 pawn with ...f5 and ...Nf6, then ...Nc6 to hit d4.
  • The knight route ...Nh6 to f5, the top engine line, attacks d4 and e3 before White sorts out the center.
  • A bishop check on b4 pins the c3 knight and makes it harder for White to win e4 back.
  • Castle quickly. Black's king is safe on g8 while White still has pawns to recover.

Plans and pawn structure

White has given a central pawn for open lines, but the c4 pawn does little and d4 needs constant protection. If Black holds e4 with ...f5, White plays f3 to break up Black's pawns and open the f-file. If Black prefers to return the pawn, ...Nh6-f5 and ...Bb4+ build pressure on d4 and win time. In both cases Black gets an easy position with a safe king and targets on d4 and c4.

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 −0.77: a clear edge for Black. Its three top choices for White:

  1. −0.77 4.Be3 Nh6 5.Nc3 Nf5 6.Nxe4 Bb4+
  2. −0.81 4.Nc3 f5 5.Be3 Nf6 6.f3 Nc6
  3. −0.94 4.Ne2 f5 5.Be3 Nf6 6.Nbc3 Nc6

Pawns, from White's side.

How it scores on lichess

350 rated lichess games reached this position; White scored 46.4%.

1200–159940.5%
1600–199947.2%
2000 and up51.7%

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

How to play against it

As Black, take on e4 and keep developing. Use ...f5 or the knight trip to f5 to keep White busy, and do not grab more pawns with your queen. As White, know that the engine prefers Black clearly here: if you play it, aim for Be3, Nc3 and f3 and hope for practical chances.

Questions

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

The French Defense: Diemer-Duhm Gambit Accepted starts 1.e4 e6 2.d4 d5 3.c4 dxe4. Its ECO code is C00.

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

Stockfish 17.1 rates the position −0.77 at depth 20, which is a clear edge for Black. In 350 lichess games from our sample, White scored 46.4%. A dubious surprise weapon; Black players who know ...f5 and ...Nh6-f5 are happy to see it.

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

White offers the e4 pawn with 3.c4 to get fast development and open lines. Black keeps or returns the pawn with ...f5 or ...Nf5 and gets a comfortable, safe position.

What should White play next?

The engine's first choice is Be3, with Nc3 and Ne2 close behind. 4.Be3 defends d4 and develops, the most natural way to keep the position together a pawn down.

Updated October 2026. Sources and method.