Knight Defense, Alekhine Gambit

After 5. Bg5 h6 6. Bh4, Black departs from the usual QGD restraint and plays 6...dxc4 at once, without waiting for White to spend a tempo on Bd3. The capture leaves Black a pawn ahead but with doubled c-pawns. The c- and d-files are half-open, and White keeps a lone central pawn on d4. The gambit label means White does not hurry to regain the pawn, preferring to seek activity in return. The line is a rarely chosen branch of the Knight Defense.