P - B 4 was the right move. It would have led to complications, in which Black might have held his own; at least, White's play would be very difficult. The text move accomplishes nothing, and puts Black { 85} in an altogether defensive position. The veiled threat B × Kt; followed by Q - R 4 ch; is easily met.
The fact that Black has now to move his Bishop back clearly demonstrates that Black's plan of development is faulty. He has lost too much time, and White brings his pieces into their most attacking position without hindrance of any sort.
The alternative was Kt - Q 4. Otherwise White would play Q - R 3, and Black would be forced to play P - K Kt 3 (not P - K R 3, because of the sacrifice B × P), seriously weakening his King's side.
White has no longer an attack, but he has compelled Black to create a marked weakness. Now White's whole plan will be to exploit this weakness (the weak K P), and the student can now see how the principles expounded previously are applied in this game. Every move is directed to make the weak King's Pawn untenable, or to profit by the inactivity of the Black pieces defending the Pawn, in order to improve the position of White at other points.
13. B × B Q × B 14. O - O R - B 3 15. K R - K 1 Kt - Q 3 16. R - K 2 B - Q 2
{ 86} At last the Bishop comes out, not as an active attacking piece, but merely to make way for the Rook.
17. Q R - K 1 R - K 1 18. P - Q B 4 Kt - B 2
A very clever move, tending to prevent P - B 5, and tempting White to play Kt × B, followed by B × P, which would be bad, as the following variation shows: 19 Kt × B, Q × Kt; 20 B × P, Kt - Kt 4; 21 Q - Kt 4, R × B; 22 P - K R 4, P - K R 4; 23 Q × R, P × Q; 24 R × R ch, K - R 2; 25 P × Kt, Q × P. But it always happens in such cases that, if one line of attack is anticipated, there is another; and this is no exception to the rule, as will be seen.
Apparently the best way to meet the manifold threats of White. B P × P would make matters worse, as the White Bishop would finally bear on the weak King's Pawn _viâ_ Q B 4. { 87}
20. R × Kt P - K Kt 3 21. Q - R 4 K - Kt 2 22. Q - Q 4 P - B 4
Forced, as White threatened P × K P, and also Q × P
Q - Q 3 was better. But Black wants to tempt White to play P × P, thinking that he will soon after regain his Pawn with a safe position. Such, however, is not the case, as White quickly demonstrates. I must add that in any case Black's position is, in my opinion, untenable, since all his pieces are tied up for the defence of a Pawn, while White's pieces are free to act.