Chess Openings Lab
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Blackmar-Diemer Gambit Declined: Lamb Defense

The Lamb Defense is 4...Nc6, developing the queen's knight to attack d4 instead of taking on f3. White gains space with tempo, while Black tries to keep the e4 pawn for now and looks for ...e5 or ...e6 to free the position.

Moves
1.d4 d5 2.e4 dxe4 3.Nc3 Nf6 4.f3 Nc6
ECO
D00
Engine
−0.22 · level (Stockfish 17.1, depth 20)
Played
417 games in our lichess sample
White scores
48.9%

Key ideas for both sides

White

  • 5.d5 kicks the knight at once. After 5...Ne5 6.fxe4 White has won back the pawn with a big center.
  • Then Nf3 trades off the e5 knight and the queen recaptures on f3, as in the main engine line.
  • 5.Bb5 pins the knight to the king and plans Bxc6+ to damage Black's pawns.
  • Be3 protects d4 but is slower, since ...Bf5 lets Black hold e4.

Black

  • Against 5.d5, the knight goes to e5 and ...e6 attacks the d5 pawn at once.
  • Trading on f3 with ...Nxf3+ and then ...exd5 opens lines for Black's pieces.
  • After 5.Bb5, take on f3 and play ...e6 and ...Be7 to finish development fast.
  • If White plays slowly, ...Bf5 and ...e6 hold the e4 pawn and keep the extra material.

Plans and pawn structure

Black's knight on c6 blocks the c-pawn, so the normal ...c5 break is gone and Black relies on ...e5 or ...e6. White's best try is space: d5 drives the knight away, fxe4 regains the pawn, and White gets a broad e4 and d5 center. Black answers by trading the e5 knight on f3 and undermining d5 with ...e6. In the Bb5 lines, the doubled c-pawns after Bxc6+ give White a long-term target on the queenside.

What the engine plays from here

Stockfish 17.1 at depth 20 rates the position −0.22: level. Its three top choices for White:

  1. −0.22 5.d5 Ne5 6.fxe4 e6 7.Nf3 Nxf3+
  2. −0.52 5.Bb5 exf3 6.Nxf3 e6 7.Bg5 Be7
  3. −0.82 5.Be3 Bf5 6.d5 Nb4 7.Bb5+ c6

Pawns, from White's side.

How it scores on lichess

417 rated lichess games reached this position; White scored 48.9%.

under 120051.9%
1200–159946.7%
1600–199948.5%

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

How to play against it

Push 5.d5 right away. The knight on c6 is a target, and fxe4 next move wins the gambit pawn back without further investment. Do not play passively with Be3 or Nge2, because ...Bf5 lets Black hold e4 and you stay a pawn down. White scores 48.9% overall in this line.

Questions

What are the moves of the Blackmar-Diemer Gambit Declined: Lamb Defense?

The Blackmar-Diemer Gambit Declined: Lamb Defense starts 1.d4 d5 2.e4 dxe4 3.Nc3 Nf6 4.f3 Nc6. Its ECO code is D00.

Is the Blackmar-Diemer Gambit Declined: Lamb Defense good for Black?

Stockfish 17.1 rates the position −0.22 at depth 20, which is level. In 417 lichess games from our sample, White scored 48.9%. A tricky sideline for Black that rewards quick play, but White equalizes easily with the d5 push.

What is the main idea of the Blackmar-Diemer Gambit Declined: Lamb Defense?

Black ignores the f3 pawn and attacks d4 with the knight. The cost is that White can push d5 with tempo and then take back on e4, so the gambit pawn is usually returned.

What should White play next?

The engine's first choice is d5, with Bb5 and Be3 close behind. 5.d5 gains space with tempo against the c6 knight, and fxe4 on the next move recovers the pawn.

Updated October 2026. Sources and method.