10. Kt-QB3 Q-B4 11. QKt-K4 Castles QR
This is imperative. If Black retires the Bishop from his unsafe position, White permanently prevents Black from castling, which is bound to be fatal in view of the open K file—e.g. 11. … B- Kt3; 12. PxP, R-KKt1; 13. P-KKt4, Q-Kt3; 14. KtxB, PxKt; l5. B- Kt5, RxP; 16. Q-B3 with a violent attack.
12. KtxQB
If White tries to win the exchange in the following way: 12. P- KKt4, Q-K4!; 13. Kt-KB3, Q-Q4; 14. PxP followed by Kt-B6, Black can initiate a promising counter attack by 14. … BxP!!; 15. PxR-Q, RxQ; 16. Kt-B6, QxKt; 17. QxQ, BxQ. In this case White exposes his King’s side by P-KKt4 in order to benefit from the unstable position of the Black KB, but unless care is taken, he can easily fall a victim to an attack on the open KKt file
12. … PxKt 13. P-KKt4 Q-K4
Not Q-Q4, on account of PxP and Kt-B6.
14. PxP KR-Kt1 15. B-R6
This is Marshall’s innovation. It gets the Bishop out of play, as P-Kt5 must necessarily follow, yet the pawn at Kt7 holds the Black Rook, and there is a permanent threat of Kt-B6 either winning the exchange or, if the Knight is taken, giving White a pair of formidable passed pawns.
15. … P-Q6 16. P-B3 B-Q3
This is quite to White’s liking, since he wishes to advance Ids centre pawns. Black’s only chance of escaping disaster would be: B-K2, with R-Q2, Kt-Q1-B2. Instead of this, his next few moves do not reveal any concerted plan, and he loses in a surprisingly short time.