The Opposition
The most important concept in king-and-pawn endings — the geometric position of two kings facing each other on the same file with one square between them, and how the side without the move-tempo is forced to step aside.
The opposition is the single endgame concept that, once learned, transforms king-and-pawn endings from guesswork into geometry. Two kings face each other on the same file with one square between them, and the side that is forced to move must step away — the kings cannot occupy adjacent squares, so one must yield. The side with the opposition is the side whose opponent is on move; the side without it is the side on move. Everything in pawn endings flows from that simple zugzwang.
What opposition is
In the diagrammed position, the white king is on d4 and the black king on d6. The two kings are on the same file, two ranks apart, with one square — d5 — between them. They cannot move closer because no king can attack another. So whichever player is on move must step his king off the d-file, freeing the king’s diagonal for the opposing king to advance.
If White is on move here, he plays — say — 1.Kc4. Black now plays 1…Kd5, advancing one rank. White must yield again; Black gains another rank. The side with the opposition gains ground on every move.
This zugzwang is not a coincidence of the position; it is a logical necessity of king moves. Whenever two kings face each other with one square between them, the side not on move has gained the opposition, and the consequence — that the other king must yield — is automatic.
Direct, distant, diagonal
Three flavours of opposition appear in practice.
Direct opposition. The two kings are on the same file or same rank, one square apart. This is the canonical case and the one that decides almost every K+P vs K position. Above is direct opposition on the d-file.
Distant opposition. The two kings are on the same file (or rank), three or five squares apart. The principle is the same — the side not on move has the opposition — but here the proof goes through one or two preliminary “echoes”. If kings are on d2 and d6, the player not to move will eventually gain direct opposition by mirroring the opponent’s king moves. Distant opposition is decisive in long-march K+P vs K positions where the kings start far from each other.
Diagonal opposition. The two kings are on the same diagonal, with one or three squares between them on the diagonal. The same zugzwang logic applies — the side on move must yield — but the yielding pattern is rotated. Diagonal opposition matters when the action is on the corner of the board or when the side trying to gain opposition cannot reach the file directly.
In all three cases the rule is identical: the side not on move has the opposition. The variations are about which square configurations count as opposition, not about who benefits.
Opposition in K+P vs K
The reason the opposition matters in K+P vs K is that the side controlling the opposition controls the key squares. The attacking king cannot reach a key square unless it can get past the defender’s king, and getting past requires forcing the defender’s king to step aside — which is precisely what gaining the opposition does.
In the position above, after 1…Kc6 (or 1…Ke6), White plays 2.Ke5, gaining ground on the e-file (or c-file by symmetry). After 2…Kd7 3.Kf6 Ke8 4.Ke6, White has the opposition again and is on the sixth rank — a key square. The pawn now advances with support, and the technique converts.
The reverse case — the defender with the opposition — is the drawing technique. If Black achieves the opposition with his king in front of the white pawn, White cannot force progress and the position is drawn by repetition.
Counting the squares
The practical trick for getting the opposition in a long-distance K+P vs K race is to count the squares between the two kings, including their own squares, along the file or rank or diagonal. If the total is odd, the side not on move has the opposition. If the total is even, the side on move has it (because moving will leave the opposition with him).
For kings on d2 and d6 (same file): the squares between, inclusive, are d2, d3, d4, d5, d6 — five squares, odd, so the side not on move has the opposition. For kings on d2 and d8 — seven squares, also odd, same conclusion. For kings on d2 and d5 — four squares, even, side on move has the opposition.
This counting is the entire heuristic. The player who can do it in his head reliably will win or hold every K+P vs K position the board offers — provided he is not playing a rook pawn, which has its own exception.
The opposition is one of those concepts whose explanation takes a full essay but whose application takes a single glance at the board. After a hundred or so K+P vs K positions, the geometry becomes automatic; the player no longer counts but simply sees that the kings are or are not in opposition and acts accordingly.