Cochrane defense

The Cochrane defense is a method for the side with only a king and rook against a king, rook, and bishop. Although this ending is usually drawn with perfect play, defending it can be highly demanding.

The central idea is to place the defending rook on the same horizontal row or vertical column as the attacking bishop and king, with the bishop between them. The rook then pins the bishop: moving the bishop would uncover a check on its own king. This pressure prevents the attacking pieces from coordinating freely to confine the defending king.

The setup works best in the central area. As a theoretical guide, the pin is normally established on one of the four central vertical columns or one of the four central horizontal rows, with at least two rows or columns between the kings. The defending king answers the enemy king's advance by moving in the opposite direction and avoiding a drive toward the edge.

Reaching one static picture is not enough. The rook must retain checks and mobility, and the defender must know when to rebuild the setup after the attacker breaks the pin. Near a corner, the available space shrinks and the method may stop working.