Bastions

Bastions are projecting elements of fortifications that extend outward from the main enceinte. They flank the curtain walls and provide fields of fire along adjacent walls, reducing blind spots and enabling enfilading fire on attackers attempting to approach the fortification.

The concept emerged in the Italian Renaissance as artillery made conventional high-walls vulnerable. Bastions became central components of the trace italienne, later called star forts, and were widely adopted across Europe and the Middle East from the 16th century onward.

Typically, a bastion consists of two faces that meet at an angle and enclose a shoulder with two flanks along the outer edge. The adjacent parapet provides fire from positions on the bastion, while the inner curtain connects bastions to the main enclosure. This arrangement permits enfilading fire along the curtain and reduces exposure for the fortress as a whole.

With changes in artillery and warfare, bastions became standard features of fortifications through the early modern period, and many survive as monumental relics. In modern usage, the term also denotes a strong defensive position or a person or institution that defends a particular principle.

In computing and networking, a bastion host is a dedicated gateway server that sits between an internal network and external networks, enforcing security policies and providing controlled access.