Rook and bishop versus rook ending

In this pawnless ending, one side has a king, rook, and bishop, while the other has a king and rook. Most normal positions are drawn with correct defense, but some placements are won and practical defense can be extremely demanding.

The stronger side tries to coordinate all three pieces and push the defending king toward an edge. The rook cuts off horizontal rows or vertical columns, the bishop controls diagonals, and the king occupies entry squares. The immediate goal is usually not checkmate, but a gradual reduction of the king's space until the defending rook becomes passive.

The defender needs an active rook. Checks from enough distance keep the attacking king from approaching comfortably, while attacks on the bishop can gain time. In the Cochrane defense, the rook pins the bishop in front of its king and keeps the kings separated. In the second-rank defense, the king and rook preserve a formation that prevents the attacking king from coordinating freely.

A theoretical draw does not mean that every move draws. Known winning formations can arise near the edge, including the Philidor and Lolli positions. Some forced wins require up to 59 moves. This interacts with the 50-move rule, which allows a draw claim after 50 moves by each player without a pawn move or capture; in this pawnless ending, only a capture resets the count.

This ending is materially similar to the rook and knight versus rook ending, but the bishop controls long diagonals and creates different restricting methods.