English Opening · A13

Agincourt Defense, Catalan Defense, after 3... b6

1. c4 e6 2. Nf3 d5 3. g3 b6 4. Bg2 Bb7 5. O-O

White's kingside bishop takes the long diagonal and Black's queenside 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. c4 Fights for d5 from the flank - contesting the centre without committing a centre pawn. Theory calls this the English Opening.
• 1... e6 Supports the centre, adding control of d5. Theory calls this the Agincourt Defense.
• 2. Nf3 Develops the knight to f3, eyeing d4 and e5.
• 2... d5 Stakes a claim in the centre, controlling e4, and frees the bishop and queen.

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