Crownwork

A crownwork is an element of the trace italienne system of fortification and is effectively an expanded hornwork (a type of outwork).

It consists of a full bastion with the walls on either side ending in half bastions from which longer flank walls run back towards the main fortress.

[2] The crownwork was used to extend the fortified area in a particular direction, often in order to defend a bridge, prevent the enemy occupying an area of high ground, or simply strengthen the overall fortifications in the expected direction of attack.

[3]