The Queen's Indian Defense arises after ... b6 on move three. Black prepares to develop the queen's bishop on the long diagonal, and fights for the e4-square with pieces instead of occupying the center with pawns.
1. d4 ♞f6 2. c4 e6 3. ♘f3 b6
White plays 3. ♘f3 instead of 3. ♘c3 to avoid the pin ... ♝b4, and the Queen's Indian is Black's flexible answer. The setup is solid and has the reputation of being one of the most reliable replies to 1. d4. The bishop on b7 and the knight on f6 both aim at e4, and Black keeps the choice between several pawn structures for later.
A typical development in the main line looks like this. White plays g2-g3 and puts the bishop on g2 to contest the long diagonal. Black completes the kingside first, and then jumps with the knight to e4.
1. d4 ♞f6 2. c4 e6 3. ♘f3 b6 4. g3 ♝b7 5. ♗g2 ♝e7 6. O-O O-O 7. ♘c3 ♞e4
Black's bishop on b7 faces White's bishop on g2, and the knight on f3 blocks the diagonal between them. If that knight moves, the diagonals open and the bishops come into play. For this reason both sides keep an eye on the squares e4 and e5.
The bishop on b7 and the knight on f6 both watch e4, so White finds it hard to build the center with e2-e4. White's usual answers are to support the advance with ♘c3, ♕c2 and ♗d3, or to neutralize the pressure by trading Black's pieces. Black does not put a pawn in the center at once, and decides later between ... d5, ... d6 and ... c5.
... ♞e4 attacks c3 and d2 and offers a trade. Black exchanges on c3 to relieve the cramp caused by White's space, and the recapture decides the pawn structure. ♕xc3 keeps White's pawns intact, while bxc3 gives White doubled pawns but a half-open b-file.
The main break for Black is ... c5, which attacks d4 and opens the c-file. ... d5 is the other central break, and it gives the position a Queen's Gambit Declined character. White's breaks are d4-d5, which gains space when Black has played ... c5, and e2-e4, which needs the support of the knight and queen.
The light squares are the key feature of the opening. White fianchettoes and Black fianchettoes, and the fight for e4 and e5 shapes most of the middlegames.
After 3... b6 White has several fourth moves. The most common are 4. g3, the Fianchetto Variation; 4. a3, the Petrosian System; and 4. e3, which develops quietly. 4. ♘c3 allows 4... ♝b4, and 4. ♗g5 pins the knight before Black has castled.
1. d4 ♞f6 2. c4 e6 3. ♘f3 b6
4. g3 prepares ♗g2, which aims at b7 and stakes a claim to the long diagonal. Black has two main replies: 4... ♝b7, which meets the bishop directly, and 4... ♝a6, which attacks the c4-pawn.
1. d4 ♞f6 2. c4 e6 3. ♘f3 b6 4. g3
After 4... ♝b7 5. ♗g2 ♝e7 6. O-O O-O White plays 7. ♘c3, developing the knight and preparing e2-e4 and ♕c2. Black replies 7... ♞e4, and after 8. ♕c2 ♞xc3 9. ♕xc3 c5 the queen recapture has kept the pawn structure intact. 10. ♖d1 supports the d4-pawn on the d-file, and Black continues with 10... d6, completing the setup.
1. d4 ♞f6 2. c4 e6 3. ♘f3 b6 4. g3 ♝b7 5. ♗g2 ♝e7 6. O-O O-O 7. ♘c3 ♞e4 8. ♕c2 ♞xc3 9. ♕xc3 c5 10. ♖d1 d6
The position is balanced, and both sides have clear plans. White has more space and will try to advance with d4-d5 or open the center with dxc5. Black has a solid structure and a bishop on b7 that becomes active once the diagonal opens, and plays for ... cxd4 followed by ... ♞c6 or ... ♛c7.
After 10. ♖d1 Black can also take at once with 10... cxd4 11. ♘xd4. The exchange opens the c-file for Black and leaves the knight on d4 exposed to ... ♞c6 and ... ♛c7, but it also opens the diagonal for the bishop on g2.
1. d4 ♞f6 2. c4 e6 3. ♘f3 b6 4. g3 ♝b7 5. ♗g2 ♝e7 6. O-O O-O 7. ♘c3 ♞e4 8. ♕c2 ♞xc3 9. ♕xc3 c5 10. ♖d1 cxd4 11. ♘xd4
The bishop on a6 attacks c4, and the move ties White's pieces to the defense of that pawn. 5. b3 supports c4, and Black checks with 5... ♝b4+ to force 6. ♗d2. After 6... ♝e7 7. ♗g2 c6 8. ♗c3 d5 Black has a Slav-like structure and White's bishop on c3 is exposed to ... ♞bd7 and ... ♞e4.
1. d4 ♞f6 2. c4 e6 3. ♘f3 b6 4. g3 ♝a6 5. b3 ♝b4+ 6. ♗d2 ♝e7 7. ♗g2 c6 8. ♗c3 d5 9. ♘e5 ♞fd7 10. ♘xd7 ♞xd7 11. ♘d2 O-O 12. O-O ♜c8
White's usual reaction is 9. ♘e5, which attacks d7 and f7. Black exchanges with 9... ♞fd7 10. ♘xd7 ♞xd7, and after 11. ♘d2 O-O 12. O-O the rook goes to c8. White has more space and Black has a solid position. White's break is e2-e4, Black's is ... e5.
White can also defend c4 with the queen. After 4... ♝a6 5. ♕c2 c5 6. dxc5 ♝xc5 7. ♗g2 ♞c6 Black has regained the pawn with free development. White often continues with 8. ♘c3 or 8. O-O.
1. d4 ♞f6 2. c4 e6 3. ♘f3 b6 4. g3 ♝a6 5. ♕c2 c5 6. dxc5 ♝xc5 7. ♗g2 ♞c6
4. a3 prevents ... ♝b4+ and prepares ♘c3 and e2-e4. The variation is named after Tigran Petrosian. Black usually replies 4... ♝a6, attacking c4, and White defends it with 5. ♕c2, preparing to build the center with e4.
1. d4 ♞f6 2. c4 e6 3. ♘f3 b6 4. a3 ♝a6 5. ♕c2 ♝b7 6. ♘c3 c5 7. e4 cxd4 8. ♘xd4 ♝c5
Black retreats the bishop to b7 and strikes at the center with 6... c5. After 7. e4 cxd4 8. ♘xd4 ♝c5 the bishop attacks the knight, and White usually retreats 9. ♘b3. The center is open, White has a space advantage, and Black has active pieces and the bishop on b7 aimed at e4. Black can also play 4... ♝b7 5. ♘c3 d5, which leads to a game with a Queen's Gambit Declined character.
4. e3 develops modestly and prepares ♗d3 and castling, without committing the g-pawn. Black replies 4... ♝b7, and after 5. ♗d3 d5 6. O-O ♝d6 Black has a setup that resembles the Slav. White develops the queenside bishop with 7. b3 O-O 8. ♗b2 ♞bd7 9. ♘bd2, and both sides keep the central breaks in reserve.
1. d4 ♞f6 2. c4 e6 3. ♘f3 b6 4. e3 ♝b7 5. ♗d3 d5 6. O-O ♝d6 7. b3 O-O 8. ♗b2 ♞bd7 9. ♘bd2
White keeps the advance e3-e4 in reserve, and Black prepares ... c5 and ... dxc4. Black can also develop the bishop to e7 and play ... ♞e4, which keeps more tension.
4. ♘c3 allows Black to reach a Nimzo-Indian setup with 4... ♝b4, and the pin on c3 keeps both setups available for Black. White can break the pin with 5. ♕c2, preparing to recapture on c3 with the queen, or with 5. ♗g5.
After 5. ♕c2 ♝b7 6. a3 ♝xc3+ 7. ♕xc3 O-O White has the bishop pair and an intact structure, and Black has a solid position. ... ♞e4 will attack the queen, and White usually answers with 8. ♗g5 or 8. g3.
1. d4 ♞f6 2. c4 e6 3. ♘f3 b6 4. ♘c3 ♝b4 5. ♕c2 ♝b7 6. a3 ♝xc3+ 7. ♕xc3 O-O
After 5. ♗g5 ♝b7 6. e3 h6 7. ♗h4 Black can exchange with 7... ♝xc3+ 8. bxc3 d6, or play 7... g5 8. ♗g3 ♞e4. The second move order transposes into the Kasparov Variation of the Nimzo-Indian Defense.
1. d4 ♞f6 2. c4 e6 3. ♘f3 b6 4. ♘c3 ♝b4 5. ♗g5 ♝b7 6. e3 h6 7. ♗h4 ♝xc3+ 8. bxc3 d6 9. ♘d2
4. ♗g5 pins the f6-knight to the queen. Black continues 4... ♝b7 5. ♘c3 h6 6. ♗h4 ♝b4, and after 7. e3 the sharp move 7... g5 drives the bishop back. 8. ♗g3 ♞e4 then attacks both c3 and the bishop, and White usually exchanges with 9. ♕c2 ♝xc3+ 10. bxc3 d6.
1. d4 ♞f6 2. c4 e6 3. ♘f3 b6 4. ♗g5 ♝b7 5. ♘c3 h6 6. ♗h4 ♝b4 7. e3 g5 8. ♗g3 ♞e4 9. ♕c2 ♝xc3+ 10. bxc3 d6 11. ♗d3
The advance loosens Black's kingside, and Black has given up the dark-squared bishop, so White has the bishop pair. Black's compensation is the active knight and White's doubled pawns on the c-file.
White can avoid the Queen's Indian by playing 3. ♘c3 instead of 3. ♘f3, and Black can then choose between 3... ♝b4, the Nimzo-Indian Defense, and 3... d5, the Queen's Gambit Declined. After 3. ♘f3 Black has several other moves besides 3... b6: 3... ♝b4+ leads to the Bogo-Indian Defense, and 3... d5 to the Queen's Gambit Declined.
The line 4. ♘c3 ♝b4 shows how the two defenses are linked. A player who relies on the Queen's Indian must also be ready to meet 4. ♘c3 with 4... ♝b4, and a player who prefers the Nimzo-Indian must be ready for 3. ♘f3.