Short answer: The opposition is when the two kings face each other with one square between them, and the side that does not have to move holds it. Holding the opposition forces the other king to give way, which lets yours advance. Together with key squares and the rule of the square, it is the core of king and pawn endgames.
King and pawn endings look simple, and that is why they trip people up. One tempo decides them. These three ideas tell you which side is winning.
What is the opposition?
Kings can never stand on adjacent squares, so when they face each other on a file with one square between them, whoever has to move must step aside. The player who does not have to move holds the opposition.
That sounds like a disadvantage for the side to move, and it is. Chess forces you to move, so the player who runs out of useful moves first gives ground. This is called zugzwang, and it decides most pawn endings.
How do you use the opposition?
With the opposition, your king can step forward or sideways while your opponent's king has to retreat or give up a key square. Without it, you try to gain it. A handy trick is triangulation, which loses a move with the king to hand the move back to your opponent.
What are key squares?
Key squares are the squares your king must reach to guarantee the pawn promotes. For a pawn on e5, the key squares are d6, e6 and f6. If your king reaches any of them, you win whoever is to move, as long as you play accurately. If the defending king gets there first, or can hold you off, the position is usually a draw.
What is the rule of the square?
It tells you whether a lone king can catch a runaway pawn. Imagine a square drawn from the pawn to its promotion square. If the defending king can step into that square, it can catch the pawn, and if it cannot, the pawn promotes. Remember that the pawn can move two squares from its starting rank, and that it matters who is to move.
What are the exceptions?
- Rook pawns. A lone a- or h-pawn is often a draw if the defending king reaches the corner, because it cannot be driven out
- Extra pawns. Once pawns are added, the opposition is only one factor, and passed pawns, majorities and spare tempi matter too
- Rook endings. The Lucena and Philidor positions play a similar role there, deciding whether an extra pawn wins or draws
Play king and pawn endings against perfect defence
The Pawn Mastery Trainer's Endgame Lab lets you play king and pawn positions against perfect defence and learn Lucena and Philidor technique. One payment of £46.97 ($62), no subscription, works offline.
Questions people ask
What is the opposition in chess?
It is when the kings face each other with one square between them and one side does not have to move. That side holds the opposition and forces the other king to give way.
Who has the opposition?
The player who does not have to move when the kings stand opposite each other with one square between them.
What is a key square?
A key square is a square that, if your king reaches it, guarantees the pawn will promote with accurate play. For a pawn on e5, the key squares are d6, e6 and f6.
Where to go next
Read our full chess pawn structure guide, then see how a passed pawn changes a position in passed pawns in chess. If you want the opposition, key squares, the rule of the square and triangulation on printable sheets, the Pawn Mastery cheat sheets are £16.97 ($22).
