In the Fundamentals course, we learned the rule of the square. This rule helps us determine whether a lone pawn can promote before the opposing king catches it. In this lesson, we will look at a more advanced endgame: the opposing king is already inside the square, so the stronger side’s king must step in to help the pawn promote. This endgame is extremely important to master — it occurs frequently in practical play and requires precise technique to win or to hold a draw.

How can the king help the pawn to promote? By taking the right position, the king can shield the pawn from the opposing king, clearing the way for it to advance safely to the promotion square. Here is an example:

No matter where the black king is, White can promote the pawn and win the game.

Key squares

A key square is a square that, if occupied by the stronger side's king, guarantees that the pawn can promote successfully. The key squares depend on the rank of the pawn. In this level, we study pawns on the 6th rank. The key squares are shown in the diagram below:

Fundamental position with a pawn on the 6th rank

If it is White’s turn to move, the position is a draw. For example: 1.e7+ Ke8 2.Ke6 leads to stalemate. Or: 1.Ke5 Ke7 2.Kd5 Ke8 3.Kd6 Kd8! — White cannot make progress.

However, if it is Black’s turn, White wins: 1...Ke8 2.e7! Kd7 3.Kf7! — White reaches a key square, and the pawn will promote next move.

Zugzwang

This position is a classic case of Zugzwang, a situation where the side to move is at a disadvantage because every legal move makes the position worse. Zugzwang occurs most often in endgames, when there are few pieces left and the number of possible moves is limited. In pawn endings, it is especially common.

Opposition

When the two kings face each other with exactly one square between them, this is called opposition. In pawn endgames, opposition is especially powerful because it often creates Zugzwang if no useful pawn move is available. The previous diagram shows the most basic form of opposition and Zugzwang.

In opposition, the king that must move is forced to retreat or step aside, allowing the opposing king to advance or break through.

Note that opposition is not automatically winning — it is a tool. On the attacking side, it helps to reach a key square. On the defending side, it can be used to block the opponent’s king from advancing.

Examples

Click the diagram to solve the puzzle.

Click the diagram to solve the puzzle.