Chess Opening Theory/1. d4/1...d5/2. c4/2...c6/3. Nf3/3...Nf6

Slav Defence
	a b c d e f g h 8 7 6 5 4 3 2 1 8 7 6 5 4 3 2 1 a b c d e f g h
	Position in Forsyth-Edwards Notation (FEN) rnbqkb1r/pp2pppp/2p2n2/3p4/2PP4/5N2/PP2PPPP/RNBQKB1R
	Moves: 1. d4 d5 2. c4 c6 3. Nf3 Nf6
	ECO code: D11-D19 D43-D49

3...Nf6 · Modern Line

Black begins development of his minor pieces with 3...Nf6, which is invariably the best square for this knight, as it exerts control over the e4 square and adds protection to the d5-pawn.

White can respond to this move in a variety of ways:

Develop a minor piece

The most commonly played move is 4. Nc3, which continues development of minor pieces and adds some pressure to the d5-pawn. This also prevents Black from developing the light squared bishop to f5, due to the trap 5. cxd5 cxd5 6. Qb3!, where Black has to undevelop the bishop in order to prevent material losses.

White can also respond with 4. Nbd2, which is a quieter move, entering the Breyer variation. With this move, White usually will play in a more slow fashion, and try for a Catalan-like setup with an eventual g3.

Prepare to castle

White can also defend the c4 pawn and release his light squared bishop with 4. e3, though it comes at the cost of blocking in the c1-bishop. Black can either continue in a Semi-Slav like fashion with 4...e6, or get the light squared bishop outside the pawn chain with either 4...Bf5 or 4...Bg4, though in either case, Black will usually have to surrender the bishop pair.

White can also attempt to enter the Catalan with 4. g3, though this is an inaccurate move order, because Black can safely develop the bishop outside of the pawn chain with 4...Bf5, which effectively equalizes for Black, entering a Closed Catalan-like position where the light squared bishop isn't trapped behind the pawn chain.

Exchange pawns

White can also enter the delayed exchange variation with 4. cxd5, which likely enters a very drawish symmetrical position. With the knights inserted, White managed to take away some of Black's options in the normal exchange variation which would have been played a move prior.

Develop the queen

White can develop the queen to a good diagonal and simultaneously prevent ...Bf5 with 4. Qc2. This also defends the c4-pawn and maintains flexibility. White can continue in normal Queen's gambit fashion with ...Bf4/Bg5 and ...e3, or consider Catalan-like positions with ...g3 and ...Bg2.

4. Qb3 develops the queen to an active position which puts pressure on b7 and d5, thereby compelling Black to either give up the center with 4...dxc4 or shut down his bishop with 4...e6. In either case, White maintains flexibility, and similar to 4. Qc2, can also play in Queen's gambit fashion with ...Bf4/Bg5 and ...e3, or Catalan-like with ...g3 and ...Bg2.

Theory table

1. d4 d5 2. c4 c6 3. Nf3 Nf6

	4
Semi-Slav defence	Nc3 e6	∞
Slav accepted	... dxc4	⩲
Quiet variation	e3 Bf5	=
Exchange variation	cxd5 cxd5	=
Breyer variation	Nbd2 Bf5	=
	Qc2 g6	=