Diagonal opposition
Diagonal opposition is the standoff in which the two kings sit on the same diagonal with exactly one empty square between them, so the king that has to move must give ground.
Most players learn the opposition on a file, but kings can also face each other along a diagonal. Put the kings on the same diagonal with a single empty square between them, such as c3 and e5, and neither may step onto that middle square because the kings would touch. The side to move has to look for another way out. That side has lost the diagonal opposition.
The same logic as before applies: the king that is not on move keeps control. Because a king moves one step at a time in any direction, giving ground along a diagonal often means retreating to a square from which the rival king can walk forward. The player who holds the standoff then steps ahead to a square that wins space or reaches a key square.
Diagonal opposition tends to appear when both kings are cutting across the board toward a passed pawn or toward a pawn they want to attack. Spotting it helps you decide whether a king march is safe. Before you commit, check the diagonals as well as the files and ranks and ask who would be to move if the kings met.
A frequent slip is to assume that opposition exists only on files and ranks, and so to walk into a diagonal standoff on the wrong move. Another is overlooking that the standoff does not matter at all unless a pawn or a key square makes the tempo count.
It sits close to Distant opposition. Distant opposition is the long-range form of the kings' standoff: the kings share a line with an odd number of empty squares between them, and the side not on move can keep that count odd until the kings meet.
Also worth reading is Shouldering. Shouldering is a king maneuver in which one king steps into a square that cuts the opposing king off from a pawn or from the route toward it, so the opponent cannot approach.
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Related terms
Opposition is a standoff between the two kings on one file or rank with a single empty square between them; whoever does not have to move holds it, because the other king must give up ground.
Distant opposition is the long-range form of the kings' standoff: the kings share a line with an odd number of empty squares between them, and the side not on move can keep that count odd until the kings meet.
Zugzwang is the bind of having to move when standing still would be best: the player on move has only moves that weaken the position, and since passing is not allowed, the duty to move itself costs something.
A king and pawn endgame is an ending in which only kings and pawns remain, so the result depends on promotion races, king placement, opposition, and exact counting of moves.
Shouldering is a king maneuver in which one king steps into a square that cuts the opposing king off from a pawn or from the route toward it, so the opponent cannot approach.
Guides that go further
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