Agincourt Defense, Neo-Catalan Declined

The Neo-Catalan Declined arises when Black, facing White's kingside fianchetto in the Agincourt Defense, prefers the developing 4...Be7 to the pawn grab 4...dxc4, and White answers with 5. O-O. Black keeps the pawn on d5, finishes kingside development and postpones any decision about the c4–d5 tension. White, meanwhile, keeps the choice between d4, which steers the game toward Catalan structures, and a slower queenside setup. A related branch, the Early b3, plays 5. b3 before castling. ECO classifies the line under A14.

Castling with 5...O-O is by far the most common reply. Less frequent options are 5...c6, which reinforces d5 in Slav fashion, and a belated 5...dxc4, against which White scores well. The engine also rates 5...c5 highly. That move leads to the Keres Defense, 5...c5 6. cxd5 Nxd5 7. Nc3 Nc6, where the center opens and Black relies on active pieces against the pressure of the bishop on g2. The engine regards the position as roughly balanced. Play is strategic rather than forcing, and White scores somewhat better in online games.