King's Indian Defense

The King's Indian Defense, often abbreviated KID, is a hypermodern answer to 1. d4. Black fianchettoes the king's bishop and lets White occupy the center with pawns, intending to undermine that center later rather than contest it at once. The position after 3. Nc3 is the gateway to the most critical lines, since the knight supports the advance e4 while leaving White's choice of system open. Black's usual reply is 3...Bg7, followed by ...d6 and castling; 3...d6 first is a transpositional move order, while 3...d5 leads to the Grünfeld Defense, treated as a separate opening.

After 4. e4 d6 Black stakes a central claim with ...e5 or the Benoni-like ...c5. Once White resolves the tension with d5, the center locks and the game becomes a race on opposite wings: White expands on the queenside, while Black either plays ...b5 or, more typically, prepares ...f5 and a kingside pawn storm. The model is the Orthodox, or Classical, Variation, 5. Nf3 O-O 6. Be2 e5, whose main line 7. O-O Nc6 8. d5 Ne7 is the Mar del Plata Variation. There White aims for c4–c5 while Black reroutes the f6-knight to d7 and pushes ...f5, ...f4 and ...g5. The Bayonet Attack, 9. b4, introduced by Korchnoi in the 1970s, was later revived by Radjabov.

White's alternatives on move 5 differ sharply in character. The Sämisch Variation, 5. f3, named after Friedrich Sämisch, shores up e4 and lets White put a bishop on e3 without being harassed by ...Ng4, at the cost of the g1-knight's natural square; play often features opposite-side castling with Be3, Qd2 and a g4–h4 advance, and Black answers with ...e5, ...c5 (the Sämisch Gambit after 5...O-O 6. Be3 c5) or ...b5. The Four Pawns Attack, 5. f4, builds the broadest possible center but lags in development, and after 5...O-O 6. Nf3 Black's standard reaction is 6...c5. The Averbakh Variation, 5. Be2 O-O 6. Bg5, discourages an immediate ...e5, and quieter tries include the Makogonov Variation, 5. h3, and the Semi-Averbakh System, 5. Be2 O-O 6. Be3. Away from 3. Nc3, the Fianchetto Variation, 1. d4 Nf6 2. c4 g6 3. Nf3 Bg7 4. g3, shelters White's king so well that Black's customary kingside attack rarely gets going.

The defense was widely distrusted until the mid-1930s, when analysis and games by Konstantinopolsky, Boleslavsky and Bronstein rehabilitated it. Fischer, Tal and Kasparov all relied on it; Kasparov abandoned it after a series of losses to Kramnik in the early 2000s, but Nakamura, Radjabov and Ding Liren have kept it in elite practice. The positions are unbalanced and heavily theoretical, giving both sides winning chances. Engines rate the position after 3. Nc3 as roughly balanced, and results in online play are nearly even.