Bastion

A bastion is a projecting section of a fortification that extends outward from the main wall to provide defensive fire along the adjacent curtain. Its purpose is to eliminate blind spots, cover the fort's enceinte, and enable enfilade fire across approaches. Bastions are typically connected by curtain walls to form a star-shaped or polygonal fortress.

In design, a bastion usually presents two faces meeting at a salient angle, with supports such as ditches, ramparts, and casemates. The concept emerged in late medieval fortifications and matured with the trace italienne in the early modern period, emphasizing low profiles and angled projections to resist artillery and maximize firepower.

Bastions became a defining feature of European military architecture from the 16th to the 19th centuries and are prominent in many surviving fortresses and UNESCO-listed Vauban works. They remain important as historical monuments and in the study of fortification theory.

In computing, a bastion host is a dedicated gateway that provides controlled access between an external network and a private internal network. It is hardened, monitored, and typically handles authentication and auditing for connections to internal systems, reducing the exposure of the broader network.