Lesson
White to move. Main line: 1. b3 e5 2. Bb2 Nc6 3. c4 Nf6 4. Nf3 e4 5. Nd4 Bc5 6. Nxc6 dxc6 7. e3 Bf5 8. Qc2 Qe7 9. Be2 O-O-O 10. f4 Ng4 11. g3 h5 12. h3 h4 13. hxg4 hxg3 14. Rg1 Rh1 15. Rxh1 g2 16. Rf1 Qh4+ 17. Kd1 gxf1=Q+
Spassky castles queenside and immediately attacks the weakened kingside with ...Ng4 and ...h5–h4. Larsen’s 13.hxg4 accepts the knight, but opening the h-file is far more important than the captured material.
The rook sacrifice 14...Rh1! forces Rxh1, after which the g-pawn advances with tempo. Black’s queen joins on h4, and 17...gxf1=Q+ promotes while capturing the rook; White resigned in a position of overwhelming attack.
The miniature shows why pawn moves near an uncastled king are permanent. White’s f4, g3 and h3 created hooks, while Black’s opposite-side king remained safe enough to spend every tempo opening lines.