St. Petersburg 1909, Game No. 51. Lasker chooses 7) B - K Kt 5 in the Ruy Lopez and grinds down Salwe in a long ending.

1. 7.Bg5 This move appears stronger than the usual 7) R - K sq. If Black Castles now, the sequel might be 7) .... 0 - 0; 8) B X Q Kt, B X B; 9) P X P, Kt X B; 10) Kt X Kt, B X Kt; 11) B X P, Q X B; (if 11) .... B X Kt; 12) B X Q, B X Q; 13) B X P White gains a Pawn) 12) P X P, Q X P; 13) Q X Q, P X Q; 14) Kt - Q 4. The Knight is in an impregnable position, and Black's Queen's Pawn badly isolated.
2. 16.f5 White could have achieved more by 16) P - Kt 4, as he would then not have abandoned the squares K 5 and K Kt 5 to his opponent. He was tempted into the actual continuation by the consideration that an entry remained for the Rook via K B 4, and the K Kt file was open to the Queen.
3. 38.Rh4 If 38) R - Kt 4, Kt - B 3; 39) R - R 4 follows 39) .... P - Q 4; 40) B P X P, P X P; 41) R X P, B - B 3. In the actual game the continuation 38) .... P - Q 4 would fail on account of 39) B P X P, P X P; 40) Kt - B 4.
4. 40.Qf2 If he allow White to play R - B 4 before this, he will ultimately lose the K B P.
5. 56.a3 Necessary, for 56) .... R (B 2) - B 7 threatens to win the K Kt P as well as the important Q R P.