Tennison Gambit, Brigg's Trap

Brigg's Trap arises in the Tennison Gambit after the knight defense 3...Nf6, continuing 4. Nc3 Bf5 5. Qe2 Qd4. Black has kept the extra pawn and supports e4 with knight, bishop and now the queen against White's pressure from both knights and the queen on e2. The trouble with 5...Qd4 is that it takes the queen away from the d-file and the defense of the queenside and d7. This leaves the bishop on f5 short of support at the moment White checks.

The refutation is 6. Qb5+, by far the most common reply, after which White scores very heavily. The check along the a4–e8 diagonal comes together with an attack along the fifth rank on the bishop on f5, and the queen also eyes b7. Black has to interpose and give up material. The engine rates the position after 5...Qd4 as a large advantage for White, despite Black's extra pawn. Other sixth moves are far less effective. The knight jump 6. Nb5, aiming at the queen and c7, is the second choice, but its results are much closer. The quiet 6. d3 gives roughly even results. The line is mainly encountered in fast online games, where the trap is a recurring practical weapon in the gambit.