Wahls Defense

The Wahls Defense arises when Black copies White's kingside fianchetto and castling move for move, then breaks the symmetry with 5...d5 rather than continuing the mirror with ...d6. Black occupies the center with a pawn while White's d-pawn sits modestly on d3. The result is a quiet, reversed King's Indian-type position. White keeps the extra tempo but has committed to nothing beyond the basic setup. Engines judge the position as roughly balanced, and White scores somewhat better in online play.

White's most popular reply by a wide margin is 6. Nbd2, the standard King's Indian Attack follow-up, which prepares e4 to challenge the d5-pawn and steer the game toward the familiar structures of the system. 6. c3 is a slower alternative that keeps options open in the center. 6. c4 is less common but is the engine's top choice. It attacks d5 at once and gives the game a more Catalan- or English-like flavor rather than a King's Indian Attack one. 6. Bf4, developing the queen's bishop before deciding on the pawn structure, is another engine suggestion.