Chess Opening Theory/1. e4/1...c5/2. Nf3/2...d6/3. d4/3...cxd4/4. Nxd4/4...Nf6

Open Sicilian
	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/3p1n2/8/3NP3/8/PPP2PPP/RNBQKB1R
	Moves: 1. e4 c5 2. Nf3 d6 3. d4 cxd4 4. Nxd4 Nf6
	ECO code: B54
	Parent: Sicilian defence → 2...d6 → 4. Nxd4

4...Nf6

Black starts the development of their pieces, whilst also attacking the e4 pawn. When Black played 2...d6, they controlled the e5 square, thus preventing White from playing e5 and kicking away this knight. As the e4 pawn is hanging, White does not have time to play 5. c4?, setting up the Maroczy Bind, as 5...Nxe4 would follow, in which White is down a pawn for no compensation.

As a result, White must find a way to defend against this threat.

Defend with a piece

The main move by far is 5. Nc3, continuing development whilst also defending the e4 pawn. This move also gets White closer to queenside castling, whilst also eyeing the key d5-square, where this knight could be excellently placed if Black plays ...e5 at a later point. In addition, the knight also helps with a king castled on the queenside, as it helps defend against threats on the c-file.

White could also defend the pawn with 5. Bd3, though d3 is often not the best square for this bishop, and this also obstructs the queen's protection of the d4-knight, therefore if Black plays ...Nc6, White will have to trade the knight or spend a tempo defending it.

Defend with a pawn

If White insists on creating the Maroczy bind, they could try the move 5. f3, the Prins variation. By defending the pawn without blocking the c-pawn, White may still play c4.

The main response is 5...e5. This kicks away the knight, 6. Nb3, where one idea is to contest the c4 pawn with ...Be6 and ...Rc8: 6. Nb3 Be6 7. c4 Nbd7 8. Be3 Rc8 9. Nc3 Bxc4. Another is to prevent White from playing e5 so that Black may get in ...d5 and (if they like ...d4) before White clamps down on the square: 6. Nb3 d5 7. Bg5 (7. exd5?! Nxd5 8. c4 Bb4+ 9. Bd2? Ne3 ∓) d4.

Alternatively White has the zwischenzug 6. Bb5+, the Venice attack, with the goal of allowing Nf5 instead, though this gives up on the idea of c4 because Black gets to play ...a6 and ...b5 with tempo. 6...Nbd7 7. Nf5 d5 8. exd5 a6 9. Ba4 b5 10. Bb3 Nb6 =.

Leave the pawn hanging

5. Bc4, the Ginsberg gambit, is a fine continuation. Apparently dropping the e4 pawn, White intends Qh5; after which, if Black plays e6 to block the attack on f7, White has ideas of Bb5+ and Nxe6. Even trickier for Black, however, is for White to switch the move order and sacrifice the bishop with 6. Bxf7+; after 6. ...Kxf7 7. Qh5+ Kg8, 8. Qd5+ wins back the knight, and Black's king is uncastled and in danger. If Black tries to prevent this by instead going 7. ...Kf6, Black's king is completely exposed, and 8. Nc3! Nxc3? is already a forced mate for White.