Chess Opening Theory/1. d4/1...Nf6/2. c4/2...e6/3. Nf3/3...b6/4. g3

=Queen's Indian Defense=

4. g3
With this move, White decides to challenge the h1-a8 diagonal immediately and fianchetto his own light-squared bishop to counter black's.

Black can now play:

That was, until, the Modern Main Line came by:
 * 4...Bb7 (Old Main Line), a standard developing move. White can then respond with Bg2 and Nc3. The line continues: 5. Bg2 Be7 6. 0-0 0-0 7. Nc3 Ne4 8. Qc2 Nxc3 9. Qxc3. White now has a spacial advantage, but black's position is solid. Black can choose many ways for counterplay, including 9...c5 (the most common), 9...f5, or 9...Be4. These lines are known for their drawish tendencies and are currently used as drawing weapons. However, there have been developed a few ways to unbalance the play in the Old Main Line:
 * 6. Nc3, which postpones castling for the e2-e4 and d4-d5 thrusts.
 * 7. d5!?, which gives up a pawn. However, white can play 8. Nh4, threatening to regain the pawn or play Nf5. If black keeps the pawn, white gets plenty of compensation for it.
 * 8. Bd2, which defends the knight on c3 and threatens a d4-d5 push.
 * 4...Ba6, attacking the c-pawn. This is a bit of a nuisance for white, who cannot comfortably defend the pawn with the natural e2-e3 because the bishop is already committed to g2.

Also possible is:


 * 4...Bb4+, echoing the Bogo-Indian and Nimzo-Indian defences. White can interpose with the bishop or knight. However, this leaves black with a slightly passive position. Nevertheless, this is solid as well.

There are other options available, though these are less likely to be encountered:


 * 4...c5, immediately challenging the (central) d-pawn. This leads to pawn structures specific to the Benoni or to variations with a late c5 of the Queen's Indian, if both sides choose to neglect this central challenge and continue to develop
 * 4...c6, leads to a Closed Catalan variation after Black's immediate 5...d5 follow-up

Theory table
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'''1. d4 Nf6 2. c4 e6 3. Nf3 b6 4. g3'''