The Lasker Trap, from the Albin Countergambit, contains the most famous underpromotion in chess. Black's far-advanced f-pawn promotes to a knight with check — not a queen — and that single quirky detail is what wins White's queen. It's a beautiful lesson that the strongest promotion isn't always a queen.
In the Albin, if White meets the wedged d4-pawn with the careless 4.e3?! and later grabs the bishop with 6.Bxb4??, Black plays exf2+ 7.Ke2 fxg1=N+! — underpromoting to a knight with check; after 8.Rxg1 Bg4+ Black wins the queen.
After 1.d4 d5 2.c4 e5 3.dxe5 d4 Black's d-pawn jams the position. The natural-looking 4.e3?! invites disaster: 4…Bb4+! 5.Bd2 dxe3! and now if White recaptures the bishop with 6.Bxb4??, Black uncorks 6…exf2+ 7.Ke2 fxg1=N+!! — promoting to a knight, giving check. The point is exact: a queen on g1 would simply be captured and nothing special happens, but the knight check forces the king to deal with the check while leaving White's pieces loose. After 8.Rxg1 the rook is dragged to g1, and then 8…Bg4+! skewers the king to the queen on d1 — Black wins the queen. White avoids the entire trap by developing with 4.Nf3 instead of 4.e3.
6. Bxb4 — 6.Bxb4?? (ply 11) is the move that loses. White grabs the bishop, assuming the e3-pawn is just a passing nuisance, but it ignores that the pawn can crash through to f2 and then promote with check. The safe move is to deal with the position calmly — and, one move earlier, the whole line is dodged by 4.Nf3 rather than 4.e3.
White sidesteps the Lasker Trap by not playing 4.e3 against the Albin — develop with 4.Nf3 and the wedge on d4 is a problem for Black, not White. And if you do reach the trap position, the honest point is that 6.Bxb4 is the greedy error: the advanced black pawn is far more dangerous than the pinned bishop, so don't go pawn-grabbing while a passed pawn is one step from promotion.
Because only the knight gives check. If Black promotes to a queen on g1, White just takes it and there's no trap. The knight check forces 8.Rxg1, and then 8…Bg4+! skewers the king to the queen on d1, winning the queen. It's the rare case where a knight is stronger than a queen.
Don't play 4.e3 against the Albin Countergambit. The standard, safe reply is 4.Nf3, developing and leaving Black's d4-pawn as a long-term weakness rather than a battering ram. The trap only exists after the inaccurate 4.e3 followed by the greedy 6.Bxb4.
A trap only works if your opponent makes the mistake — strong players sidestep these, which is why each page also shows how to avoid it. Every line here is checked legal with the same engine the board runs, and every checkmate is verified.