3 | | | ^P | | | ^Q | | | |---------------------------------------| 2 | ^P | ^P | ^P | | | ^P | ^P | ^P | |---------------------------------------| 1 | ^R | | ^B | | ^R | | ^K | | +---------------------------------------+ a b c d e f g h

Diagram 24.

In the case illustrated above it was the Bishop who assisted the Queen.  A Knight could aid in an attack on h7 from either g5 or f6.  More frequently he does so from g5 as usually the square f6 is not accessible to him on account of the Pawn g7 protecting it.  In the majority of cases the Knight goes to g5 from f3, and the Queen attacks h7 from h5, coming from her original square d1.  Then, if Black cannot protect h7 by a Knight from f6 or by the Bishop, from f5 for instance, or from g6, the only protection as a rule is to advance the Pawn to h6.  The position of Diagram 25 may serve as an example.

+---------------------------------------+
8 | #R | #Kt| #B | #Q | #K |    |    | #R |
|---------------------------------------|
7 | #P | #P | #P | #P | #Kt| #P | #P | #P |
|---------------------------------------|
6 |    |    |    |    |    |    |    |    |
|---------------------------------------|
5 |    |    | #B |    |    |    |    |    |
|---------------------------------------|
4 |    |    | ^B | #P | ^P |    |    |    |
|---------------------------------------|
3 |    |    |    |    |    | ^Kt|    |    |
|---------------------------------------|
2 | ^P | ^P | ^P |    |    | ^P | ^P | ^P |
|---------------------------------------|
1 | ^R |^Kt | ^B | ^Q | ^K |    |    | ^R |
+---------------------------------------+
a    b    c    d    e    f    g    h

Diagram 25

Black’s last move was Kt-e7, while Kt-f6, which protects the Pawn h7 against future attacks, is generally preferable in any opening.  White can now play Kt-g5, attacking the Pawn f7 for the second time, as it is already attacked by the Bishop c4.  The student will, at this stage of his development, not yet know why Black should be so anxious to defend the Pawn f7, considering that he is a Pawn ahead so that the loss of a Pawn would only equalize the forces but would not give White a material advantage.  However, later on, when discussing the strategy of the opening, it will become evident that in the position of the diagram Black must, under all circumstances, defend the Pawn f7 as otherwise his game would soon become hopeless on account of the exposed position of his King.

There are only two ways for Black to defend f7.  One is to advance the Queen’s Pawn to d5, interrupting the diagonal of White’s Bishop; the other is to castle, so that the Rook procures the second protection for the Pawn f7 which is needed.  It would then not be good for White to capture the Pawn because he would have to give up Knight and Bishop for Rook and one Pawn, which is not a sufficient equivalent.

Of the two ways indicated only the first one is feasible.  For if Black castles he gives White an opportunity to institute an attack on the weak Pawn h7 with Knight and Queen against which Black has no satisfactory defense.  Play would develop as follows: