Q-Q2?; 12.  KtxB, followed by RxKt).  For a long time it was thought that after Kt-Q4 Black had to exchange Knights, which enables White to make the pawn at QB7 “backward” by B-K3.  For Black must first play P-KR3 to guard his Kt against the threat of P-B3 and P-KR4.  However, a sensational innovation which refutes the Kt’s move was introduced in Breslau in 1912.  It is the following sacrifice:  10. ...  Castles; 11.  Kt-Q4, KtxKP!; 12.  P-B3, B-Q3!!; 13.  PxKt, B-Kt5!!; 14.  Q-Q2, Q-R5 with an overpowering attack.

10. ...  Kt-B4 11.  B-B2 B-Kt5 12.  Q Kt-Q2 Castles 13.  Kt-Kt3 Kt-K5

Here Lasker played Kt-K3 against Janowski (Paris, 1912), but it proved to be inferior, because 14.  Q-Q3 disorganises Black’s King’s side forcibly.

The move in the text is not really a pawn sacrifice.  After 14.  BxKt, PxB; 15.  QxQ, QRxQ; 16.  KKt-Q4, KtxKt; 17.  KtxKt, R-Q4, White cannot play 18.  RxP, because of P-QB4; 19.  Kt-B2, B-B4 or 19.  Kt-B3, R-Q8ch; 20.  Kt-K1, B-B4; 21.  R-K2, B-Q6; 22.  R-K3, B-Kt4.

14.  B-B4           P-B4
15.  PxP e.p.        KtxP(B3)
16.  Q-Q3           Kt-K5?

This loses the QBP, and weakens the QP.  Black might have tried BxKt; 17.  QxB, B-Q3.  It would then have been possible to support the QP by P-B3 after moving the Kt away.  If Black was anxious to preserve his two Bishops he would even have risked P-Kt3.  After 17.  B-R6, R-B2, the Bishop could have been driven away again by the KKt from Kt1 or Kt5.  The open file offered some compensation and chances of counter attack.

17.  BxP Q-Q2

Not QxB because of QxPch.

18.  Kt-K5         KtxKt
19.  BxKt          B-R5

RxP is bad because of 20.  RxKt, B-KB4; 21.  Q-Kt3.

20.  B-Kt3         BxB
21.  RPxB          B-B4

Now RxP! was feasible with a level game after:  22.  RxKt, B-B4! 23.  KxR, BxR; 24.  Q any, Q-B4ch, followed by BxB.  After missing this chance, Black soon loses the game.

22.  Q-Q4          KR-Q1
23.  QR-Q1         Q-QB2
24.  Kt-Q2         KtxKBP

A last and desperate attempt.  Black obtains Rook and pawn against two minor pieces, but has no time to initiate an attack with the Rooks.  The wisest plan was to give up the P, with a view to effecting the exchange of the minor pieces, because an ending with Queen and Rooks generally produces a draw.  Black could not play KtxKtP instead of the move in the text because of 25.  B-Kt3!.

25.  BxB KtxR 26.  RxKt QxKtP 27.  B-K6ch K-R1 28.  BxP QR-B1 29.  Kt-K4 Q-R5 30.  P-QKt3 R-B3

White now obtains a passed pawn, and a speedy win.

31.  Q-B2 Q-R4 32.  Q-B3 QxQ 33.  PxQ P-Kt3 34.  R-Q2 R-Kt3 35.  P-QB4 PxP 36.  PxP R-Kt8ch 37.  K-B2 P-QR4 38.  P-B5 R-QB8 39.  P-B6 K-Kt2 40.  B-B4!  RxB 41.  RxR RxP 42.  R-Q7ch K-R3 43.  K-Kt3 R-B5 44.  Kt-B2 K-Kt4

Mate was threatened by:  45.  Kt-Kt4ch, K-R4; 46.  R-Q5ch, P-Kt4; 47.  R-Q6 and R-R6 mate (or if RxKtch, PxR mate).