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

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.

Practise the line

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

Your move 1 of 20/2

1.d4d5
2.Bf4

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

Common mistakes

Three that come up again and again below master level. Each is ordinary opening theory — a named trap, or the error every coach corrects — not a statistic, and not drawn from anybody's games.

Forgetting b2 once the bishop has left

1.d4 d5 2.Bf4 c5 3.e3 Qb6

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

1.d4 d5 2.Bf4 Nf6 3.e3 e6 4.Bd3 Nh5

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.
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

1.d4 Nf6 2.Bf4 g6

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.

Try it on one of your own

The board above is for the line itself; this is for a game you played. Paste a game in this opening, or pull one from chess.com, and every move is graded against what the engine would have played. Open the board, read how the grading works, or go back to the other openings.