We must now turn to the development of the pieces corresponding to these pawn skeletons.  If White plays P-K5

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

Diag. 32

on his third move, he prevents the Black KKt from reaching KB3, whence he might have moved to Q2.  This is a desirable position, from which he could support the advance of P-QB4.  But the Knight has other chances of development, to KR3 and B4, whence he can take his share in the attack on the White Pawn at Q4.  In consequence White must postpone P-KB4 in order not to intercept the action of the QB on R6.  Now, in that case White’s Pawn at his K5 has not sufficient support against the attack by Black’s P-KB3 (Diagram 31), and the latter move gives Black the advantage.  The two main variations illustrative of these considerations are: 

I

3.  P-K5 P-QB4 4.  P-QB3 Kt-QB3 5.  P-KB4 PxP 6.  PxP Q-Kt3 7.  Kt-KB3 Kt-R3

II

3.  P-K5          P-QB4
4.  P-QB3         Kt-QB3
5.  Kt-B3         P-B3

In both cases the initiative falls to Black, in the first through the attack on White’s Q4, the mainstay of White’s centre; in the second through attack on White’s K5, the White centre itself.  We must therefore consider White’s advance of P-K5 on the third move as premature.  Let us now find out whether it is advantageous to effect the same subsequently.  A developing move can be interpolated, e.g. 3.  Kt-QB3, Kt-KB3.  If White plays P-K5 now he gains time for his advance of P-KB4, as Black’s Knight must retreat.  On the other hand he cannot now maintain his pawn at Q4, as he has blocked his QBP.  We arrive at the following plan of development: 

3.  Kt-QB3 Kt-KB3 4.  P-K5 KKt-Q2 5.  P-B4 P-QB4 6.  PxP Kt-QB3

If Black were to play BxP at once, White could play Q-Kt4 with an attack on the Knight’s Pawn.  That is the object of Black’s waiting move.  White must either play 7.  Kt-B3, which prevents his Q-Kt4, or 7.  B-Q3, after which Black would take the pawn on B4 with his Knight, getting rid of the White Bishop. 7.  Q-Kt4 at once would be answered by P-B4.

7.  Kt-B3          BxP
8.  B-Q3           P-B4

Black cannot castle yet, on account of the following threat, which I give in full because it occurs frequently in practice:  8. ...  Castles; 9.  BxPch, KxB; 10.  Kt-Kt5ch, K-Kt1:  11.  Q-R5, R-K1; 12.  QxPch; 13.  Q-R5ch; 14.  Q-R7ch; 15.  Q-R8ch; 16.  QxP mate.