London System · A48

Main line, after 3... Bg7, through 4... d6

1. d4 Nf6 2. Nf3 g6 3. Bf4 Bg7 4. e3 d6

Black's kingside bishop takes the long diagonal. Bf4 gets outside the pawn chain before it closes, then the same sound setup against nearly anything: c3, e3, Bd3 - low theory, a solid centre, a quiet kingside pull.

The first 4 moves, explained

• 1. d4 Stakes a claim in the centre, controlling e5, and frees the bishop and queen.
• 1... Nf6 Develops the knight to f6, eyeing d5 and e4.
• 2. Nf3 Develops the knight to f3, eyeing d4 and e5. It also props up the d4 pawn. Theory calls this the Knights Variation.
• 2... g6 Prepares the fianchetto: the bishop will take the long diagonal via g7. Theory calls this the East Indian Defense.

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