An outwork is a minor defense, fortification

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...

, built or established outside the principal fortification limits, detached or semidetached. Outworks were developed in the 16th century, such as ravelin

Ravelin

A ravelin is a triangular fortification or detached outwork, located in front of the innerworks of a fortress...

s, lunette

Lunette (fortification)

In fortification a lunette was originally an outwork of half-moon shape; later it became a redan with short flanks, in trace somewhat resembling a bastion standing by itself without curtains on either side...

s (demilunes), caponier

Caponier

A caponier is a type of fortification structure. The word originates from the French word "caponnière" - which strictly means capon-cote i.e. chickenhouse.The fire coming from the feature A caponier is a type of fortification structure. The word originates from the French word "caponnière" -...

s to shield bastion

Bastion

A bastion, or a bulwark, is a structure projecting outward from the main enclosure of a fortification, situated in both corners of a straight wall , facilitating active defence against assaulting troops...

s and fortification curtains from direct battery. Later the increasing scale of warfare and the greater resources available to the besieger accelerated this development, and systems of outworks grew more and more elaborate and sprawling as a means of slowing the attacker's progress and making it more costly.