Agincourt Defense, Catalan Defense, Semi-Slav Defense

This variation arises when Black meets the English with ...e6, ...Nf6 and ...d5, and then answers White's fianchetto with 4...c6 instead of the more active ...c5 seen in the parent Catalan Defense. The pawns on c6, d5 and e6 form the Semi-Slav triangle. This gives d5 lasting support and blunts the bishop on g2, though it also shuts in Black's light-squared bishop. In exchange, Black is ready to take on c4 and keeps the queenside pawns flexible. The result is a sturdy but somewhat passive setup that relies on careful development rather than counterplay in the center.

White's most common reply by far is 5. O-O, which leaves the central decision for later. 5. b3 protects c4 and prepares a double fianchetto in the Réti manner, holding the d-pawn back. 5. cxd5 settles the tension at once. The engine also favors 5. d4, which heads for Catalan-type positions. It rates the position as roughly balanced, and White scores well in practice.