In the Fundamentals course, we learned the rule of the square. This rule helps us determine whether a pawn (without any assistance) can promote before the opposing king can catch it. However, in this lesson, we will explore a more complex endgame scenario: The opposing king is in the square, and the king of the stronger side must help the pawn to promote. This endgame is crucial to understand as it frequently arises in practical play and requires precise technique to convert a winning position or hold a draw.

How can the king assist the pawn in promoting? The king must position itself in such a way that it can shield the pawn from the opposing king, allowing the pawn to advance safely to the promotion square. Here is an example of how this can be achieved:

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It doesn't matter where the black king is on the board - White can promote the pawn and win the game.

Key squares

A key square is a square that, if occupied by the king of the stronger side, ensures that the pawn can promote successfully.

The key squares depend on the rank of the pawn. In this level, we are looking at a pawn on the 6th rank. The key squares are illustrated in the diagram below:

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Fundamental position with the pawn on the 6th rank

If in this position, it is White's turn to move, White cannot win. For example: 1.e7+ Ke8 2.Ke6 is stalemate. White cannot make any progress, for example: 1.Ke5 Ke7 2.Kd5 Ke8 3.Kd6 Kd8!

However, if it is Black's turn to move, White wins with 1...Ke8 2.e7! Kd7 3.Kf7!, reaching the key square. The pawn can promote on the next move.

Zugzwang

This is a situation of Zugzwang, which means that the side to move has a disadvantage because any legal move makes their position worse. Zugzwang usually only occurs in endgames, where the number of pieces and therefore the number of possible moves is reduced. In pawn endgames, Zugzwang occurs more frequently than in other endgames.

Opposition

A situation where the kings stand opposite each other (with one square between them) is called opposition. This is especially important in pawn endgames, where it can often result in Zugzwang, if no (or no good) pawn moves are available. The previous diagram is the most basic form of opposition and Zugzwang.

If the two kings are in opposition, the king which must move has to either move backwards or sidewards, allowing the opposing king to advance or circumvent it.

Note that opposition in itself is not always winning, it is just a means to move by the opponent's king when it is obstructing the way to some other goal, like reaching a key square. When defending, opposition can be used to maintain obstructing the way for the opposite king.

Examples

Click the diagram to solve the puzzle.

Click the diagram to solve the puzzle.