I shall treat at some length the various defences from which Black can choose, and in studying this most important King’s side opening, we shall have occasion to note many points of general interest for operations in the centre.

Broadly speaking, two entirely different systems of defence can be distinguished:  either Black will try to maintain his centre pawn, or else, giving up the centre, try to gain some other advantage as compensation.

Black can only maintain his centre pawn if he can prevent his QKt from being exchanged.  As is readily seen, White can attack Black’s KP a second time with P-Q4, whilst after Black’s P-Q3 any other defensive move would hinder development.  These considerations lead to the first main line of defence in which Black plays 3. ...  P-QR3.  After 4.  B-R4 Black has the option of releasing the pin by playing P-QKt4 at some opportune moment.  If White elects to exchange his Bishop for the Kt forthwith, he can remove the Black centre pawn after 4. ...  QPxB by playing 5.  P-Q4, but the exchange of the B for the Kt gives Black a free development and in consequence a good game. (Compare note to move 4 in Game No. 12.)

Diagram 22 reproduces a typical position in this defence.  The more usual continuation for White is 4.  B-R4, Kt-B3;

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

Diag. 22.

5.  Castles; he does not trouble to protect his KP as its capture would allow his Rook an open file on which to act against the opposing King (compare Games Nos. 14 and 17) 5. ...  B-K2.  Now Black can capture the KP without much risk, as the Bishop is on the King’s file. 6.  R-K1, White covers his pawn, and thereby threatens to win a pawn by BxKt.  Therefore Black must not delay playing 6. ...  P-QKt4.

After 7.  B-Kt3, P-Q3; (Diagram 22) White cannot yet execute the manoeuvre which underlies the whole tendency of the Ruy Lopez, namely P-Q4, maintaining the pressure in the centre, because after KtxQP, 9.  KtxKt, PxKt; 10.  QxP?  White loses a piece through 10. ...  P-B4, etc.  It is therefore necessary to play P-QB3 first.  White could also obtain a rapid development by Kt-B3, P-Q3, B-K3 or Kt5, but this arrangement is not popular, because