The talus is an architectural feature of some late medieval castles, especially prevalent in crusader

Crusades

The Crusades were a series of religious wars, blessed by the Pope and the Catholic Church with the main goal of restoring Christian access to the holy places in and near Jerusalem...

 constructions. It consists of a sloping face at the base of a fortified wall

Fortification

Fortifications are military constructions and buildings designed for defence in warfare and military bases. Humans have constructed defensive works for many thousands of years, in a variety of increasingly complex designs...

. The slope acts as an effective defensive measure in two ways. First, conventional siege equipment is less effective against a wall with a talus. Scaling ladders

Escalade

Escalade is the act of scaling defensive walls or ramparts with the aid of ladders, and was a prominent feature of siege warfare in medieval times...

 may be unable to reach the top of the walls and are also more easily broken due to the bending stresses caused by the angle they are forced to adopt. Siege towers cannot approach closer than the base of the talus, and their gangplank

Corvus (weapon)

The corvus or harpago was a Roman military boarding device used in naval warfare during the First Punic War against Carthage....

 may be unable to cover the horizontal span of the talus, rendering them useless. Furthermore, defenders are able to drop rocks over the walls, which will shatter on the talus, spraying a hail of shrapnel

Fragmentation (weaponry)

Fragmentation is the process by which the casing of an artillery shell, bomb, grenade, etc. is shattered by the detonating high explosive filling. The correct technical terminology for these casing pieces is fragments , although shards or splinters can be used for non-preformed fragments...

into any attackers massed at the base of the wall.