Alfil

In chess history, the alfil is a piece from shatranj, an old form of the game developed in Persia and the Islamic world. It represented an elephant and moved exactly two squares diagonally. It could leap over the intervening square even when another piece occupied it.

The historical alfil could not stop on an adjacent diagonal square or travel along an entire diagonal. Every leap kept it on squares of the same color and gave it access to only a limited part of the board. It was therefore far less mobile than the modern bishop.

This distinction is essential when reading old positions. Treating the piece as a modern bishop creates attacks and defenses that did not exist under the historical rules and may destroy the intended solution.