Part of the Sicilian Defense: see the full opening guide
The Magnus Smith Trap is named after Magnus Smith, the three-time Canadian champion of the early 1900s, and lives in the Sozin Sicilian, the setup Bobby Fischer later made his trademark. Black plays one casual fianchetto move, ...g6, at exactly the wrong moment, and White's light-squared bishop and queen combine in a two-move deflection that wins the queen. Fischer himself annotated the refutation in My 60 Memorable Games.
In the Sozin after 5...Nc6 6.Bc4, Black plays 6...g6?!, ignoring the bishop on the a2-g8 diagonal. White trades on c6 and strikes with 8.e5!. The natural 8...dxe5?? opens the d-file, and 9.Bxf7+! deflects the king (it is the only legal move) so that 10.Qxd8 wins the queen for a bishop.
After 1.e4 c5 2.Nf3 d6 3.d4 cxd4 4.Nxd4 Nf6 5.Nc3 Nc6 6.Bc4, White's bishop points at f7 and the game has become the Fischer-Sozin Attack. The thematic reply is 6...e6, blunting the bishop. Instead 6...g6?! invites the combination: 7.Nxc6 bxc6 8.e5! attacks the f6 knight, and the pawn cannot be ignored. Everything now hangs together tactically: 8...dxe5?? opens the d-file, and Black's queen on d8 is defended only by the king. So 9.Bxf7+! deflects: the king must take (9...Kxf7 is literally the only legal move, since d7 is covered by the queen down the open file and e7 is blocked by Black's own pawn), and 10.Qxd8 scoops the queen. Nothing recaptures on d8: the f8 bishop blocks the h8 rook, and the f6 knight does not reach d8. White has won queen for bishop.
8… dxe5 — 8...dxe5?? (ply 16) is the losing move, opening the d-file with the queen still on it. Fischer's verdict was blunt: correct is 8...Ng4, keeping the damage to a bad structure. The earlier 6...g6?! is what invited everything: it did nothing about the c4 bishop's stare at f7, and that bishop is the engine of the deflection.
As Black in the Sozin, remember the granite rule: meet 6.Bc4 with 6...e6, so the bishop bites on granite and Bxf7 tricks disappear. If you have played 6...g6 and White uncorks 8.e5, do not open the d-file: play Fischer's 8...Ng4 and grovel a little (Lasker defended 8...Ng4 9.e6 f5 against Schlechter in their 1910 world championship match and held). The pattern to burn in: open d-file plus bishop on c4 equals Bxf7+ followed by Qxd8.
No. Magnus Smith (1869-1934) was a three-time Canadian champion, and the Sozin Sicilian even carries a Magnus Smith Variation in the opening books. Chess historian Edward Winter argues the trap's name is a misnomer historically, but the label has stuck for over a century.
Fischer gives 8...Ng4 as correct, and Lasker showed the defensive method with 8...Ng4 9.e6 f5 against Schlechter in their 1910 world championship match, eventually holding a draw. Black stands worse but fights on. 8...Nh5? fails too: Fischer analyzes 9.Qf3!, when g4 and Ne4 follow and Black's queen ends up trapped.
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.