the Queen being so much more powerful than the Rook, the process is far easier and shorter. These are the three elementary endings and in all of these the principle is the same. In each case the co-operation of the King is needed. In order to force a mate without the aid of the King, at least two Rooks are required.
2. PAWN PROMOTION
The gain of a Pawn is the smallest material advantage that can be obtained in a game; and it often is sufficient to win, even when the Pawn is the only remaining unit, apart from the Kings. It is essential, speaking generally, that
the King should be in front of his Pawn, with at least one intervening square.
If the opposing King is directly in front of the Pawn, then the game cannot be won. This can best be explained by the following examples.
Example 5.
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