Queen's Gambit Declined: Modern Variation, Knight Defense
The Knight Defense is 4...Nbd7 against the Modern Variation, guarding f6 with a second piece instead of breaking the pin with ...Be7. White usually exchanges with cxd5 for a Carlsbad structure, while Black keeps ...c6, ...Be7 and ...Nf8 ideas, plus a well-known trap on d5.
- Moves
- 1.d4 d5 2.c4 e6 3.Nc3 Nf6 4.Bg5 Nbd7
- ECO
- D51
- Engine
- +0.26 · level (Stockfish 17.1, depth 20)
- Played
- 512 games in our lichess sample
- White scores
- 49.4%
Key ideas for both sides
White
- 5.cxd5 exd5 fixes the Carlsbad structure; then e3, Bd3 and a later Bf4 retreat keep the bishop useful.
- Do not grab d5 with the c3 knight after the pawn trade. That is the Elephant Trap and it costs a piece.
- 5.Nf3 with Bh4 after ...h6 keeps the pin and leads to Orthodox-style positions with Qc2.
- In Carlsbad lines, plan Rb1 with b4 and b5, or Nge2 with f3 and e4.
Black
- The d7 knight sets the Elephant Trap: Nxd5 is met by ...Nxd5, and if Bxd8, ...Bb4+ wins the queen back.
- After cxd5 exd5, play ...c6, ...Be7 and route the knight via f8 to g6 or e6.
- Against Nf3 and e3, ...h6, ...Be7, ...O-O and a later ...c5 free the position.
- The c8 bishop wants ...Bf5 or ...b6 and a bishop on b7; plan its route before it gets stuck.
Plans and pawn structure
With ...Nbd7 in, Black's queen knight supports f6 and the e5 or c5 breaks, but it blocks the c8 bishop. White usually exchanges on d5 and plays e3, Bd3 and Nge2 or Nf3, then pushes b4 and b5 or f3 and e4. Black reroutes the knight from d7 to f8, plays ...c6 and looks for ...Ne4 or ...Bf5 to trade the bishop on d3. Without the exchange, Black aims for ...c5 once castled.
Where the engine's main line heads: Carlsbad structure (after cxd5 exd5). The Carlsbad structure, from cxd5 exd5: White has d4 and no c-pawn, Black has c6 or c7 and d5 and no e-pawn.
What the engine plays from here
Stockfish 17.1 at depth 20 rates the position +0.26: level. Its three top choices for White:
- +0.26 5.cxd5 exd5 6.e3 c6 7.Bd3 Be7
- +0.20 5.Nf3 h6 6.Bh4 Be7 7.e3 O-O
- +0.13 5.e3 Be7 6.Nf3 O-O 7.Qc2 c5
Pawns, from White's side.
How it scores on lichess
512 rated lichess games reached this position; White scored 49.4%.
Light: White wins. Grey: draws. Dark: Black wins. About the sample.
Traps and pitfalls
Elephant Trap (Black sets it)
White takes the d5 pawn with 6.Nxd5, trusting the pin on the f6 knight. Black breaks the pin with 6...Nxd5, and after 7.Bxd8 Bb4+ White must give the queen back, ending up a piece down.
Where it goes next
- Cambridge Springs Defense, Argentine Variation5.e3 · rare
- Rochlin Variation5.Nf3 · rare
How to play against it
As White, take 5.cxd5 exd5 and develop with e3 and Bd3. Never take d5 with the knight while the bishop on g5 can be hit by ...Bb4+. As Black, keep the trap in mind but focus on the ...Nf8 regroup.
Other lines with this name
The lichess opening list also files these lines under the same name, though they reach a different position: 1.d4 d5 2.c4 e6 3.Nc3 Nf6 4.Bg5 Nbd7 5.e3; 1.d4 d5 2.c4 e6 3.Nc3 Nf6 4.Bg5 Nbd7 5.e3 c6.
Questions
What are the moves of the Queen's Gambit Declined: Modern Variation, Knight Defense?
The Queen's Gambit Declined: Modern Variation, Knight Defense starts 1.d4 d5 2.c4 e6 3.Nc3 Nf6 4.Bg5 Nbd7. Its ECO code is D51.
Is the Queen's Gambit Declined: Modern Variation, Knight Defense good for Black?
Stockfish 17.1 rates the position +0.26 at depth 20, which is level. In 512 lichess games from our sample, White scored 49.4%. A sound choice for Black with a built-in trap for impatient White players, though the c8 bishop takes time to develop.
What is the main idea of the Queen's Gambit Declined: Modern Variation, Knight Defense?
Black defends the pinned knight with ...Nbd7 and keeps the bishop flexible. White usually exchanges on d5 for a Carlsbad structure and must avoid the Elephant Trap.
What should White play next?
The engine's first choice is cxd5, with Nf3 and e3 close behind. 5.cxd5 fixes the pawn structure before Black can choose ...c6 or ...dxc4 on better terms.
Related lines
Updated October 2026. Sources and method.