Opposition — what it means in chess
Kings facing off with one square between; the side not to move holds the advantage.
Kings facing off with one square between; the side not to move holds the advantage.
[[board startfen="8/8/3k4/8/3K4/8/3P4/8 b - - 0 1" pgn="Kc6 Ke5 Kd7 Kd5 Ke7 Kc6 Ke6 d4" caption="Kings face off with one square between them — and Black, forced to move first, must give way. White outflanks, takes the front squares, and the pawn follows." notes="Direct opposition: kings one square apart on the same file, and the player who must move loses ground. Black is on move. Black steps aside — every king move surrenders something. White immediately takes the diagonal route forward. Not the pawn: the king. The pawn wins this endgame last, not first. Black rushes back to block the path. White retakes the opposition. Same standoff, one rank higher — and again Black must blink first. Black tries the other side. White outflanks on the opposite wing. The king now controls the squares in front of the pawn. Black trails the escort. Now, and only now, the pawn moves. With the king clearing the road two ranks ahead, the promotion walk is routine — the game was decided by the kings alone."]]
Opposition is the standoff of kings: same rank, file, or diagonal, an odd number of squares between them — most often exactly one — and the player who does not have to move holds it. Kings cannot approach each other, so whoever must step first surrenders squares. In king-and-pawn endgames, that single tempo decides more games than any tactic.
The position above is the whole curriculum in nine plies. Black must move, so White's king marches — not straight, but outflanking: each time Black blocks, White retakes the opposition a rank higher, and Black must yield again. Notice what the pawn does for the first eight plies: nothing. The strongest habit this endgame teaches is that the king leads and the pawn arrives, because the pawn's advance without the king's escort throws away winning positions that the kings had already settled.
The Endgame Society glossary defines more than 240 chess terms — rules, notation, tactics, strategy, pawn structures, endgames, and openings — in language a beginner can act on rather than dictionary shorthand.