Ravelin

A ravelin is a triangular fortification or detached outwork, located in front of the innerworks of a fortress (the curtain walls and bastions).

It originated from small forts that were supposed to cover the bridge that led across the moat to the city or fortress gate from a direct attack.

However, it was not until the German fortress builder Daniel Specklin (1536–1589) recognized the principal importance of ravelins (which he still called "ledige Wehr" or "revelin").

The Italian origins of the system of fortifications (the star forts) of which ravelins were a part gave rise to the term trace Italienne.

The French 17th-century military engineer Vauban made great use of ravelins in his design of fortifications for Louis XIV, and his ideas were still being used in 1761 by Major William Green at Gibraltar.