Chess Opening Theory/1. e4/1...d5/2. exd5/2...Nf6/3. c4/3...e6/4. dxe6

With 4. dxe6 White accepts the pawn. Black can recapture the pawn while developing their bishop, and though they will be a pawn down, they will have two minor pieces developed already while White has none. Black hopes to transform their development lead and the open lines in the middle of the board into a successful attack.

After 4...Bxe6, developing the bishop, 5. d4 is the main move. White takes control of the centre and prepares to develop their queenside pieces. Then, the main move is 5...Bb4+, though 5...Nc6? is a trap for the unwary.

The main way to meet 5...Bb4+ is to offer the trade of bishops, 6. Bd2, and the main continuation is 6...Qe7 (defending the bishop) 7. Bxb4!? Qxb4+ 8. Qd2 (offering queen trade) Nc6 (defending the queen) 9. d5 (apparently forking the knight and bishop) O-O-O (pinning the d5 pawn to the queen)⩱. The queen trade, 9. Qxb4?!, is worse for White (9...Nxb4 [threatening ...Nc2+] 10. Na3 O-O-O∓).

The engine line for White is not to trade bishops and simply 7. Be2, sheltering the king. If 7...Bxc4?, taking the pawn while pinning c4's defender, 8. Qa4+! Nc6 9. Bxb4 Qxb4+ 10. Qxb4 Nxb4 11. Bxc4±.

Interrupting the check with 6. Nc3!? is inaccurate on account of 6...Ne4, increasing pressure on the knight and threatening to win back the pawn and an exchange besides (...Nxc3 bxc3 Bxc3+ Bd2 Bxa1). 7. Ne2, defending c6, is the best move, but this interrupts White's bishop's vision of c4 and so returns the pawn to Black ...Bxc4 and the game is equal.

Therefore it is often more palatable for White to play 7. Qd3?!, defending c6 and the pawns, but this is inaccurate on account of 7...Bf5, x-raying the queen through Black's knight. As an example, the game Kruszynski v Dejkalo, 1987^[1], continued 8. Bd2 O-O 9. O-O-O Nxc3 10. Qxf5 Nxd1 11. Bxb4 Qxd4 12. Bxf8 Nxf2 (threatens ...Qd1#) 13. Be2-+. 8. Qe3??, to step out of the x-ray, walks into other tactics on the e-file, e.g. 8...O-O 9. Bd2 Nxc3 10. bxc3 Re8!.

5...Nc6? is the start of a provocative but unsound trap. The idea is, after 6. d5!, forking Black's bishop and knight, Black can lay a trap with 6...Bc5, targeting f2. Black has apparently sacrificed a minor piece, but it is too dangerous for White to take. 7. dxe6? Bxf2+ 8. Ke2 (White's king must move but cannot step away from the queen, else lose it) Bd4 and White may be up in material but they have no opportunity to convert their advantage. White's pieces are too passive, their king too vulnerable, and the position too open to defend. An illustrative miniature is 9. exf7+ Kxf7 10. Nf3 Qe7+, and Black has mate in four.

Though exciting, the line is unsound thanks to 6. Nc3!, which helps to defend the queen on d1, after which Black's minor pieces are still hanging. This can still be tricky: 6...Ng4 and White must defend f2 before taking, else 7. dxe6?? Bxf2+ 8. Ke2 Nd4+ 9. Qxd4 Qxd4-+.

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

1. e4 d5 2. exd5 Nf6 3. c4 e6 4. dxe6

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