London System
One setup against almost everything: d4, Bf4, e3, c3, Nf3, Nbd2 and Bd3. Easy to learn, very solid, and far more dangerous than its quiet reputation once the knight lands on e5.
The London System gets its name from the 1922 London tournament, where Capablanca, Alekhine and Rubinstein all used it, although James Mason had played it since the 1880s. For a long time it was seen as a harmless way to avoid theory; today Carlsen, Kramnik, Caruana and Kamsky use it at the highest level and it is one of the most popular openings online. White's plan is the same against nearly every defence: the dark-squared bishop comes out to f4 before e3 shuts it in, the pawns form a pyramid on c3, d4 and e3, and the pieces aim at the kingside. The price of that consistency is a few recurring weak spots, above all the b2 pawn once the bishop has left c1, and the f4 bishop itself when ...Bd6 or ...Nh5 challenges it.
The ideas in 7 positions
Click a card to see it on the board. 0/7 viewed
Choose your path
White's setup stays the same; Black chooses the structure, and that decides where the fight happens.
Common mistakes, by level
Real patterns from club games. Every line is engine-checked; in the evals, plus is good for White.
Middlegame plans
What to do once the book runs out.
Now make it stick
Reading is the easy part. Solve the real mistakes from this opening until the patterns fire by themselves.
Sources: Wikipedia: London System (history, setups, Jobava London, notable games) · Wikibooks: Chess Opening Theory, 1.d4 d5 2.Bf4 (CC BY-SA) · Our own puzzle database: most frequent punished mistakes in London System positions (Lichess games, both players rated 1800+) · Stockfish 19, depth 20 on every mistake; every idea, variation and plan line checked move by move at depth 16
Bishop out before e3
Move 1 of the line — press → or waitThe whole point of the London: the dark-squared bishop gets outside the pawn chain before e2-e3 locks it in, which is exactly the problem White has in many Queen's Gambit lines. Playing 2.Bf4 at once (the Accelerated London) also avoids some of Black's sharpest replies to 2.Nf3.