Opposition in Chess: What It Is and How It Wins Endgames

Opposition in chess is the position in which the two kings face each other on the same file, rank or diagonal, with one square —or an odd number of squares— between them. The side that does not have to move has the opposition: the other king is forced to step aside and let it through. It is the idea that decides almost every king and pawn endgame, and you can learn it in an afternoon.

Why the side not to move wins

In the middlegame, having the move is an advantage: each move is a tempo to improve something. In pawn endgames the opposite is often true. Kings can never stand on neighbouring squares, so when they face each other with one square between them, neither king can occupy that middle square. The side to move cannot go forward: it can only step sideways or back, and either way it opens the road for the enemy king.

Being obliged to move when every move makes things worse is called zugzwang, and the opposition is its most common form. That is why the same king and pawn versus king position can be a win or a draw depending on who is to move.

Here the kings are on e4 and e6, with e5 in between. If Black is to move, the king has to step aside and the white king outflanks on the opposite side: after ...Kd6, Kf5 (Kd4 also wins); after ...Kf6, Kd5. The white king advances, takes the opposition again further up the board —for example ...Kd6 Kf5 Ke7 Ke5— and eventually reaches the squares that decide the ending. If White is to move in the same position, Black answers every king move by stepping in front again (Kd4 Kd6, Kf4 Kf6) and the pawn does not get through.

Three forms: direct, diagonal and distant

• Direct opposition. The kings on the same file or rank with one square between them. This is the one you meet in games and need to recognise instantly.
• Diagonal opposition. The kings on the same diagonal with one square between them. It is mostly a stepping stone: when the other king moves, the diagonal turns into direct opposition.
• Distant opposition. The kings on the same line but further apart, with three or five squares between them. You take it while the kings are still far away, so that you arrive with the direct opposition when they come closer.

All three come down to the same count: an odd number of squares between the kings, with the other side to move. If the number of squares is even, the side to move has the opposition, because it can take one step and make it odd.

Key squares and the king on the sixth

The opposition is not an end in itself: it is the way to bring your king to the pawn's key squares. These are the squares from which the attacking king always wins, whoever is to move.

For a pawn that has not yet crossed the middle of the board (rook's pawns aside), the key squares are the three two ranks in front of the pawn: with a white pawn on e4, they are d6, e6 and f6. Once the pawn is on the fifth rank, the three squares on the rank directly ahead are key squares too. If the king reaches one of them, the ending is won and the opposition no longer matters.

The clearest case is the king on the sixth rank in front of its pawn:

If Black is to move, ...Kf8 allows Kd7 and the pawn promotes untroubled. If White is to move, Kd6 Kd8 e6 Ke8 e7 Kf7 Kd7 and the pawn promotes as well. All the earlier work —taking the opposition, outflanking— is aimed at getting here.

How the weaker side defends

For the defender, the rule is the same seen from the other side: stand in front of the pawn and take the opposition every time the enemy king approaches. If the attacking king cannot reach a key square, the ending is a draw.

The defence also has an endpoint worth knowing: when the pawn reaches the seventh rank with check, the defending king stays on the promotion square, and if the attacker steps in front, it is stalemate. With the white king on d6, a pawn on e6 and the black king on d8, White to move, e7+ Ke8 Ke6 is stalemate: a draw. That resource saves a huge number of positions that looked lost.

And there is one exception to know by heart: the rook's pawn. With a pawn on the a or h file, a defending king that reaches the promotion corner almost always draws, even if the attacker has the opposition, because the stronger king has no room to outflank.

White can push the pawn or manoeuvre with the king, but as long as the black king stays in the corner, the ending ends in stalemate or a lost pawn.

Distant opposition in a real position

Distant opposition is the part people forget, and it is what wins while the kings are still far apart. In this position the pawn is a long way from both kings and what matters is who dominates the centre:

After Ke4 the kings are on the e file with three squares between them, and it is Black to move. Any other White move —king or pawn— lets the win slip. We checked it with a complete analysis of king and pawn versus king: it is the only winning move.

The practical way to find these moves is to count: if the kings are on the same file and the number of squares between them is odd, the side to move is at a disadvantage. Before moving your king in a pawn ending, count.

With more pawns on the board, distant opposition generalises into corresponding squares: pairs of squares where, if one king stands on one, the other must stand on its partner. The classic example is the 1901 study by Emanuel Lasker and Gustavus Reichhelm:

The solution is found with the method of corresponding squares rather than brute-force calculation: every time the white king steps onto a square, the black king must be able to step onto its partner, and the winning move is the one that leaves Black without a partner available. It is a study for when simple opposition is already second nature.

The rule of the square

The other tool that goes with the opposition is the rule of the square, which answers a different question: can the king catch a pawn running alone to promote? Picture a square with one side running from the pawn to its promotion square. If the defending king can step into that square on its move, it catches the pawn; if not, the pawn queens.

The a5 pawn's square runs from a5 to d8. With Black to move, ...Kd5 steps into it and the pawn falls. With White to move, a6 shrinks the square (now a6 to c8) and the king on e4 no longer gets there. Two caveats: if the pawn is still on its starting square, count the square from the rank in front, because it can advance two squares; and if your own king blocks the path, the rule fails and you have to calculate.

Typical mistakes

• Pushing the pawn too early. An advanced pawn takes squares away from its own king and hands the defender tempi. King first, pawn second.
• Taking the opposition without looking at the key squares. The opposition is the means; the goal is to reach d6, e6 or f6 (or whichever key square applies). If you can get there directly, you do not need it.
• Forgetting stalemate. With the defending king on the promotion square, one careless king move by the attacker ends in a draw.
• Ignoring the rook's pawn. Winning with it requires keeping the defending king out of the corner; once it gets there, no technique helps.

How to study it

Opposition is learned at the board, not by reading. Set up the positions in this article and play them from both sides —once with White to move and once with Black to move— and notice what changes. Then play them against an engine until they come without thinking.

It is the first of the endgames you must know and the foundation for everything that follows: rook and pawn versus rook endings also often come down to a battle of kings. And since pawn endings are won by whoever understands the pawn structure, it pays to study them together.

If you want to work on endgames as part of a plan, the course Evaluation, structures and attack devotes one of its stages to typical endgame mistakes, and Modern chess logic explains why endgames are always won by the same players. And if you cannot see why an ending slipped away in one of your own games, you can ask a GM.