Black being behind with his development is already threatened by sacrificial combinations.  If he takes the Bishop he loses by 15.  B-Kt5ch, K-B1; 16.  Q-Q8ch!, BxQ; 17.  R-K8 mate, or l5. ...  P-B3; 16.  BxPch, and so on.

14. ...              P-B3
15.  Q-K4            B-K3
16.  R-K3            B-QB4

Here Black might have castled on the Queen’s side, but R-Q1 would have had much the same sequel as in the actual game.

17.  B-K5            Q-R3
18.  R-Kt3           B-KB1

A sorry retreat.  But after Q-Q7, which may have been Black’s original intention, White plays R-KB1, threatening B-KB4.

19.  R-Q1

This move completes White’s development, and only seems to give Black a chance of castling.  However, Black has no satisfactory continuation.

19. ...                  Castles?
20.  QxPch               PxQ
21.  B-R6                Mate

Game No. 21

White:  Eduard Lasker.  Black:  Aljechin.

Three Knights’ Defence.

1.  P-K4 P-K4 2.  Kt-KB3 Kt-QB3 3.  Kt-B3 B-Kt5 4.  Kt-Q5

Developing another piece by B-Kt5 or B4 would be more in accordance with principle.

4. ...  B-K2

There was a threat of KtxB and KtxP.  If Black plays P-Q3, the B must retire all the same after 5.  B-Kt5.  It seems best to retire the B to K2 rather than to B4 or R4, because there remains the threat of a pin subsequently by B-KKt5, which might become serious with the Knight at Q5.

5.  B-B4 Kt-B3 6.  P-Q3 P-Q3 7.  KtxB QxKt 8.  P-B3 P-KR3

The KKt is to support the advance of P-Q4 subsequently, and that is why Black does not want to allow it to be pinned.  This is sound strategy, since White has exchanged his QKt, which from B3 prevents P-Q4 in the ordinary way.

9.  B-K3 Castles
10.  Q-Q2 B-K3
11.  B-Kt3

The first mistake.  B-QKt5 should be played to retard P-Q4.

11. ...                BxB
12.  PxB               P-Q4

---------------------------------------
8 | #R |    |    |    |    | #R | #K |    |
|---------------------------------------|
7 | #P | #P | #P |    | #Q | #P | #P |    |
|---------------------------------------|
6 |    |    | #Kt|    |    | #Kt|    | #P |
|---------------------------------------|
5 |    |    |    | #P | #P |    |    |    |
|---------------------------------------|
4 |    |    |    |    | ^P |    |    |    |
|---------------------------------------|
3 |    | ^P | ^P | ^P | ^B | ^Kt|    |    |
|---------------------------------------|
2 |    | ^P |    | ^Q |    | ^P | ^P | ^P |
|---------------------------------------|
1 | ^R |    |    |    | ^K |    |    | ^R |
---------------------------------------
A    B    C    D    E    F    G    H

Diag. 132