Chess Opening Theory/1. e4/1...d5/2. Nf3

White sacrifices their e-pawn in the hopes of a potential lead in development. The Tennison gambit may arise out of the Scandinavian defence or Zukertort opening.

2...dxe4, accepting the gambit, is usual and most critical. This attacks White's knight, so 3. Ng5, counter-attacking the e-pawn and pressuring f7 is the main move. White can leverage this pressure into a lead in development before recovering the pawn, or lay a number of traps for Black, especially if they get too invested in holding onto the extra pawn. Black is typically advised to accept the gambit then give the pawn back with 3...e5.

To decline the gambit, 2...Nc6 3. exd4 Qxd4 keeps things in Scandinavian territory or Black has several transpositions to choose from:

• 2...e5? transposes into the dubious Elephant gambit.
• 2...e6 transposes into a French defence, e.g. 3. exd5 exd5 4. d4 is an Exchange French.
• 2...c6 transposes into a Caro-Kann, e.g. the Two knights attack with 3. Nc3, or an Exchange Caro-Kann after 3. exd5 cxd5 4. d4 Nc6.

Declining with 2...Nf6 allows 3. e5 Nfd7 4. d4, and White has an easier game with central space.

Pushing the pawn 2...d4?!, hoping to cramp White's position, loses a pawn against best play. One line is 3. c3 c5 4. cxd4 cxd4 5. Qa4+! Nc6 6. b4 and b5 is coming, and the knight can't keep defence of the d-pawn. 6...Nf6 7. b5 Qa5 8. Qxa5 Nxa5 9. Nxd4±.

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

1. e4 d5 2. Nf3

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Wikipedia has related information at Tennison Gambit.