Rook vs Bishop: The Safe Corner Draw

Watch the method: press play to see the winning idea run, or step through it move by move.

Rook versus bishop, no pawns, looks like a formality for the rook. It is a draw from almost everywhere, and the entire theory of the ending compresses into an estate agent's slogan: location. The defending king wants the corner whose color its own bishop cannot touch.

Why the mismatched corner holds. Trapped on h8 with a light-squared bishop, the defender always has the g8 interposition against the back-rank check. Capturing the bishop lets the king recapture with a trivial draw, and maintaining the pin backfires spectacularly: the pinned bishop cannot move, the king has no squares, and the defender is stalemated on the spot. The rook can win a tempo anywhere on the board except the one place it needs to.

Why the matching corner loses. Put the same king in a corner of the bishop's own color and the stalemate evaporates: the bishop now occupies the king's breathing square instead of guarding it, zugzwang arrives, and the rook collects the bishop or mates. One diagonal of difference separates a fortress from a funeral.

Practical value: this is the standard last-ditch save when an exchange goes down in a simplified position, and knowing WHICH corner to run to must be automatic, because the run starts many moves before the fortress forms. The attacker here never gives up a half point and will punish a single misstep of the bishop, which is the lesson: the fortress is solid, but only its exact furniture holds it up.