English Opening · A14

Agincourt Defense, Neo-Catalan Declined, after 1. Nf3, through 6... c5

1. Nf3 d5 2. g3 Nf6 3. Bg2 e6 4. O-O Be7 5. c4 O-O 6. b3 c5

White's kingside bishop takes the long diagonal. c4 fights for d5 without committing the centre pawns: White often fianchettoes and plays a reversed Sicilian with an extra tempo.

The first 4 moves, explained

• 1. Nf3 Develops the knight to f3, eyeing d4 and e5. Theory calls this the Zukertort Opening.
• 1... d5 Stakes a claim in the centre, controlling e4, and frees the bishop and queen.
• 2. g3 Prepares the fianchetto: the bishop will take the long diagonal via g2. Theory calls this the King's Indian Attack.
• 2... Nf6 Develops the knight to f6, eyeing d5 and e4. It also props up the d5 pawn.

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