Openings · A45 / D02

London System

The same setup against nearly anything: d4, Bf4, e3, c3, Bd3, Nbd2, O-O.

1.d4 d5 2.Bf4played as White

Play it through on the board below.

Practise the line

You play White; the other side answers on its own. Nothing here is saved or graded.

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Your move 1 of 20/2
  1. 1.d4d5
  2. 2.Bf4

Your move. Drag a piece, or tap it and then its square.

The idea

The bishop leaves the pawn chain before e3 shuts it in, and the rest is a system rather than a line — the same six or seven moves against most of Black's replies. That is the appeal: it is cheap to learn and hard to punish.

The cost is that it is not automatic. The two things that make the setup work are the bishop on f4 and the pawn on d4, and both have well-known ways of being taken away.

Common mistakes

Three that come up again and again below master level: named traps and the errors every coach corrects.

Forgetting b2 once the bishop has left

After 3…Qb6
  1. 1.
  2. 2.
  3. 3.
The mistake
Playing the setup without a plan for …Qb6, which hits b2 and d4 at once.
Why it costs
It is the standard way to argue with the London and it comes on move four. Choosing there and then, over the board, is how a comfortable system turns into a bad position.
Instead
Know your answer in advance. 4.Nc3 lets the pawn go for a strong initiative — 5.Nb5 comes with threats — while 4.Qc1 or 4.Qb3 keep everything defended and the game quiet.

Losing the bishop to …Nh5

After 4…Nh5
  1. 1.
  2. 2.
  3. 3.
  4. 4.
The mistake
Letting Black trade the f4 bishop off with …Nh5 without deciding anything about it.
Why it costs
That bishop is the point of the system. Handing it over for a knight leaves the dark squares around d4 and e5 thin, and the remaining pieces have nothing in particular to do. The engine still has White slightly ahead here, so this is not a blunder; it is a trade that costs the system its purpose if it happens without a plan.
Instead
Bg5 keeps it; Bg3 accepts the trade but opens the h-file for you after hxg3. Either is a decision. Losing it for nothing is not.

Playing it on autopilot against …g6

After 2…g6
  1. 1.
  2. 2.
The mistake
Reaching for the same setup when Black fianchettoes, so the bishop on f4 has nothing to look at.
Why it costs
With …g6, …Bg7 and …d6, Black's structure leaves the f4 bishop biting on air, and …Nh5 comes with tempo. The system's whole selling point — that it works against everything — is the thing that goes wrong.
Instead
Change plan: Nc3 and e4 (the Barry Attack) is the family answer to a King's Indian setup, and puts the pawns where the bishop's diagonal is worth something.

In real games between beginners

  • 1 in 59games end with White giving checkmate by move 15. In all openings: 1 in 33.
  • 1 in 130games end with White getting checkmated by move 15. In all openings: 1 in 54.

From 22,646 Lichess games in this opening between players rated under 1200, blitz and slower, September 2026. How we counted.

What the engine says

After 1.d4 d5 2.Bf4, these are Black's six best moves according to Stockfish, with the bar showing Black's chance of winning. The whole list sits within 3 percentage points of win chance: none of them is a mistake, and the choice is about the positions you want to play.

  1. c5+0.1
  2. Bf5+0.1
  3. Nf6+0.1
  4. e6+0.2
  5. g6+0.2
  6. a6+0.3

The engine's main line from c5: c5 e3 Nc6 Bb5 cxd4 exd4 Bf5 Nf3.

Stockfish 18, depth 24. Scores are in pawns from White's side. Another engine or depth will move individual numbers a little; the picture does not change. How we check.

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