The Diagonal Opposition

When you start learning endgames, one of the first and most important things you encounter is the opposition. The occurs when the two kings are directly facing off (‘opposed’) with one square in between them, and one must give way to the other. The player whose turn it is not, has the opposition. It looks something like this:

With Black to play – meaning White has the opposition – they must step aside and allow White’s king to gain ground, eg. …Kd7 Kf6, and with this technique the pawn will strut through to promotion. If Black had the opposition instead – that is, if it were White’s move – White would not be able to make progress, as the black king quite literally shadows White’s: Kf5 Kf7 Ke5 Ke7 Kd5 Kd7, until White reluctantly pushes the pawn, which is a textbook draw.

The opposition is so important because it’s one of the top tools for promoting a passed pawn, which decides a significant number of endgames. And it doesn’t end with the basic opposition! Consider now: the diagonal opposition.

Black must give up their pawn, yet draws with …Kg7!, taking the diagonal opposition where the kings are separated by one square on a diagonal. Really, this just means that Black is ready to take the regular opposition, Kxf5 Kf7 and we are in the exact same circumstance as above, where Black has the opposition and draws by following the white king. They should not play the hasty …Kf7?? Kxf5 and White wins.

As a winning method, it would look like this:

Kd5! is the only winning move, intending …Ke7 Ke5 with the opposition, or having the favourable king placement in any case. Of course not Ke5?? in the diagram, when Black gets to play …Ke7 and draw.

There is also something more nebulous called the distant opposition, the exploration of which is left to the reader. When you understand these, you will find endgames as a whole make a lot more sense!