London System

1.d4 d5 2.Nf3 Nf6 3.Bf4

The same eight moves against almost anything: bishop to f4, then e3, c3, Nbd2, Bd3, castle. No theory to memorise — you learn one structure deeply and let your opponent make the mistakes.

Spar this opening

Your setup

Bishopf4 / g3
Knightf3
Knightd2
Bishopd3 / e2
Pawnsd4 e3 c3
CastleO-O

Bf4 before e3. The one rule of the London: bishop OUT before e3, or you lock it behind your own pawn — the exact bad bishop the system exists to avoid.

Ideas

Bishop out before e3

Bf4 first. Then e3. Never the other way round.

e3 is coming no matter what, and once it's played the c1-bishop can't get out. Playing Bf4 first costs nothing and puts your best piece on its best diagonal, staring at c7 and the queenside.

The pawn triangle c3–d4–e3

d4 is the centre; c3 and e3 hold it up. That's the whole structure.

With c3 and e3 in, nothing Black does to d4 works: …c5 and …Nc6 can hit it, but it's defended twice and the bishop has c2 to retreat to. A solid centre means you can spend your other moves on development and a plan.

When they offer to trade your bishop, say no

…Bd6 offers a swap. Step back to g3 — the bishop is the soul of the London.

Black's dark bishop is their most awkward piece; yours is your best attacker. Trading them hands Black easy equality. Bg3 keeps the diagonal, and if Black ever takes on g3, hxg3 gives you a sturdy structure and an open h-file.

…Qb6 hits b2 — defend calmly

The queen on b6 eyes your b-pawn. Qb3 (after c3) or Qc1 (before it) and carry on.

…c5 and …Qb6 is Black's sharpest try: two attackers on d4 and one on b2. It looks scary but it isn't — Qb3 offers a queen trade that leaves you with the better structure, and Qc1 simply guards b2. Don't play Nc3 to defend it unless you know the trap.

The plan: a knight on e5, then the kingside

Once set up, plant a knight on e5, aim Bd3 and the queen at h7, and push f4.

Your structure points at Black's king. Ne5 is supported by d4 and can be recaptured by the other knight from d2 (via f3). With Bd3 on the b1–h7 diagonal and Qf3 or Qe2 behind it, f4 and sometimes g4 roll forward. The e4 break is the other plan once …c5 has been dealt with.

…Nh5 chases the bishop

Retreat Bg3. If they take it, hxg3 is a fine structure with an open h-file.

The knight on h5 is out on a limb: it defends nothing and blocks Black's own h-pawn. After Bg3 Nxg3 hxg3 your pawns are doubled but solid, your rook has the h-file, and Black has spent three knight moves for nothing.

Against …g6: same setup, plus h3 and Be2

Fianchetto setups want …Nh5 and …Bg4. h3 stops the bishop; Be2 keeps yours safe.

When Black fianchettoes, their bishop on g7 looks at your queenside and their knights want g4 and h5. h3 denies g4, Be2 (instead of Bd3) doesn't get hit by …Nh5–f4 tricks, and c3 blunts the long diagonal. Then Nbd2 and castle as usual.

The structure

The London System: an easy, repeatable setup (Bf4, e3, c3, Nbd2). White plants a knight on e5, eyes the b1–h7 diagonal, and can build a kingside attack.

Traps

The …Qb6 trap (Nb5!)

d4 d5 Nf3 Nf6 Bf4 c5 e3 Qb6 Nc3 Qxb2 Nb5

The tell: Black's queen comes to b6 hitting b2 before you've played c3.

5.Nc3 dares Black to take b2. After …Qxb2 6.Nb5! threatens Nc7+ forking king and rook, and Rb1 traps the queen. Only play it if you remember 6.Nb5 — otherwise Qc1 is the safe answer.

Model games

Main setup vs …d5

d4 d5 Nf3 Nf6 Bf4 e6 e3 c5 c3 Nc6 Nbd2 Bd6 Bg3

You build the trademark Bf4, e3, c3, Nbd2 structure and keep the bishop with Bg3, aiming a knight at e5 and your pieces at the kingside.

Black hits back with …c5 and …Qb6

d4 d5 Nf3 Nf6 Bf4 c5 e3 Nc6 c3 Qb6 Qb3 c4 Qxb6 axb6

Black's sharpest try hits b2 and d4. Qb3 offers the trade; after …c4 Qxb6 axb6 you have the healthier structure.

vs a King's-Indian setup

d4 Nf6 Bf4 g6 Nf3 Bg7 e3 O-O Be2 d6 h3

Get the bishop out early, settle into your structure, and add h3 to deny Black's pieces the g4-square.

Move-order twin (1…Nf6 first)

d4 Nf6 Nf3 d5 Bf4 e6 e3 c5 c3 Nc6 Nbd2 Bd6 Bg3

The moves arrive in the other order and from move 4 the position is identical. The London doesn't depend on the sequence.

How the coach grades a move

Every move you play gets one of six grades, from the engine’s view of the position, with the book’s verdict taking over when it is harsher. The sentence beside it is always the reason. Tap it for what the move did, why this opening wants it, and whether anything was better.

Best: Nothing better was available.
Good: Within a few percent of best. Noise at this depth.
Playable: A small real gap. The better move is named, play goes on.
Inaccuracy: Seven to twelve points of winning chances. The game stops to show you.
Mistake: Twelve or more, or a move the book warns against, or a broken order rule.
Blunder: Twenty-five or more. Usually material.

Catalogued as D02 / A48 in the Encyclopaedia of Chess Openings, the reference index most databases sort by.