White plays (1) Q-h5, and if Black makes an indifferent move he mates through (2) Qxh7+, Kxh7; (3) R-h5.

Black could try to defend himself with (1) ..., P-g6.  White can then continue with (2) Q-h6 and again Black cannot make an indifferent move such as P-d6 for instance, as White would have another mate in two moves, namely (3) R-h5 (threatening Qxh7), Pxh5; (4) Q-f6.

More frequent than the mate with Rook and Knight shown above is one which usually occurs in the end game and which is illustrated in Diagram 28.

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

Diagram 29.

White plays Kt-f6+ and Black cannot go with the King into the corner as the Rook would mate him on h7.  After K-f8 White draws the game through perpetual check; for after (2) Kt-h7+, K-e8; (3) Kt-f6+ the King must go back to f8 as on d8 he would be mated by R-d7.  Consequently White can check the King indefinitely on h7 and f6.

An example for the cooperation of Rook and Bishop is shown in Diagram 29.  White plays B-f6, and there is no way for Black to prevent the mate threatened through R-h3 followed by R-h8.

It is evident that the force of the Rooks will increase as the board gets emptier through the exchange of men, for they will then find more open lines to act in.  One of the most important lines for Rooks to occupy is—­especially in the ending —­the one in which most of the attackable Pawns of the opponent are standing, that is in the majority of cases the second or the seventh rank respectively.  If both Rooks cooperate with each other in this rank they usually decide the victory within a short time.

Following is an example which is taken from a master game.  As far as the material is concerned the players are about even, as the Queen is worth as much as the two Rooks while Knight and Bishop are an approximate equivalent of the Black Rook and the Pawn which Black is ahead.  The Pawn a4 is rather dangerous for White, as he needs only three more moves to reach the first rank where he can be promoted into any piece.  On the other hand the Rooks doubled in the seventh rank give White so strong an attack on the Black King that he forces the mate before Black succeeds in realizing the advantage of his advanced passed Pawn.