Chess Opening Theory/1. e4/1...d5/2. Nf3/2...dxe4/3. Ng5

From g5 White's knight attacks e4 and pressures f7, the most vulnerable square in Black's position.

After 3...Nf6!?, defending e4, White can first turn their pressure on f7 into a development lead before recovering the pawn, or hope to entrap Black with it.

• 4. Bc4 (threatens 5. Bxf7+ Kd7) e6□ 5. Nc3 Nc6 6. Ngxe4.
• 4. d3?! sets the groundwork for the Intercontinental Ballistic Missile variation.^[1] 4...exd3 5. Bxd3 and the common move 5...h6?? is a blunder: 6. Nxf7 Kxf7 7. Bg6+ Kxg6 8. Qxd8 wins the queen for two minor pieces.

It is also dangerous for Black to hold onto the extra pawn too tightly.

• 4. Nc3 Bf5 5. Qe2? and Black should give back the pawn, happy knowing that White's queen is misplaced and exploitable. Otherwise, 5...Qd4?? walks into Brigg's trap: 6. Qb5+! Bd7 7. Qxb7 (threatens Qxa8) Bc6?! (defends the rook through the queen) 8. Bb5! (pins the bishop). At best Black is losing the rook, at worst:
  • 8...Qb6??^[2] 9. Qc8#.
  • 8...Qd7 9. Bxc6 Qxc6??^[3] 10. Qc8#

Black can sidestep the tricky lines by returning the pawn, 3...e5 4. Nxe4 f5 and 5. Ng3 is usual, though the surprising 5. d4!, sacrificing the knight, is superior by engine:

• 3...e5 4. Nxe4 f5 5. d4! fxe4 6. Qh5+!
  • 6...g6?? allows 7. Qxe5+ Qe7 8. Qxh8 and White is up the exchange.
  • 6...Ke7?? allows 7. Bg5+ skewering the queen. 7...Nf6 8. dxe5 (attacking the pinned knight) wins back the material. 8...Qd4!? is an interesting try, defending f6 through the pawn, but 9. exf6+ gxf6 and the critical move is 10. Nc3!, giving up the bishop sacrifice but preparing Rd1. 10...fxg5 11. Qxg5+ Ke8 12. Rd1 and the threat is Qd8#.
  • Therefore 6...Kd7□ 7. Qf5+ and Black's best line is to repeat moves and draw, otherwise 7...Kc6 8. Qxe4+ Kd7 9. dxe5 Ke8⩲.

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

1. e4 d5 2. Nf3 dxe4 3. Ng5

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