Chess Opening Theory/1. d4/1...Nf6/2. c4/2...g6/3. Nc3/3...Bg7/4. e4/4...d6

The move d6 ensures that White can't kick the Black Knight with e5. It also prepares to play e5 or c5 at some point. White has a variety of sharp choices:

5. Nf3, the Classical or Orthodox variation, results in a race on opposite sides: White tries to break through on the queenside before Black's forces get to the White king. Having taken the lion's share of the centre, White must now develop their minor pieces and castle. After 5...O-O 6. Be2, Black tries for the 6...e5 pawn break, and how White responds leads to the next major branching point of the theory. 5. Nf3 is by far the most popular line. This is commonly also played in the mover order 5. Be2 O-O 5. Nf3.

After 5. f3, the aggressive Sämisch variation, is the chief sideline. White will normally castle queenside (although castling kingside can also occur) and attack along the h-file. After 5...O-O 6. Be3, Black chooses between the 6...e5 pawn break, as in the classical variation, or 6...c5, the tactical Sämisch gambit.

5. f4, the Four Pawns attack, is the most megalomaniacal variation. White gains even more space with a fourth pawn in on the fourth rank. Black must react quickly to avoid getting crushed by White's centre, but in the long term they can exploit the weak squares the advancing pawns has left behind. This is the most popular sideline at the amateur level.

5. h3 is the quirky Makogonov variation, which stops a knight from getting into g4 while retaining the option of Nf3.

5. g3, the Deferred fianchetto, is the most positional variation. Normally the position is fluid. Black usually exchanges his e-pawn for White's d-pawn, Black tries to play on the queenside dark squares and against e4, while White lines his forces up against d6 and the kingside.

5. Nge2 is the Kramer variation. 5. Nge2 intends Ng3, keeping the option of f3, similar to the Sämisch.

For explanation of theory tables, see theory table and for notation, see algebraic notation..

1. d4 Nf6 2. c4 g6 3. Nc3 Bg7 4. e4 d6

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Wikipedia has related information at King's Indian Defence

• Kasparov, Garry, & Keene, Raymond 1989 Batsford chess openings 2. ISBN 0-8050-3409-9.

• 365Chess. 1. d4 Nf6 2. c4 g6 3. Nc3 Bg7 4. e4 d6
• chessgames. 1. d4 Nf6 2. c4 g6 3. Nc3 Bg7 4. e4 d6