Here are some definitions:
fort (fôrt, frt)
1. A fortified place or position stationed with troops.
2. A permanent army post.
[Middle English, strength, stronghold, from Old French, strong, strength, from Latin fortis; see bhergh-2 in Indo-European roots.]
1. (Military / Fortifications) a fortified enclosure, building, or position able to be defended against an enemy
hold the fort Informal to maintain or guard something temporarily
[from Old French, from fort (adj) strong, from Latin fortis]
Noun 1. fort – a fortified military post where troops are stationedfort – a fortified military post where troops are stationed
military post, post – military installation at which a body of troops is stationed; “this military post provides an important source of income for the town nearby”; “there is an officer’s club on the post”
armed forces, armed services, military, military machine, war machine – the military forces of a nation; “their military is the largest in the region”; “the military machine is the same one we faced in 1991 but now it is weaker”
2. fort – a fortified defensive structurefort – a fortified defensive structure
alcazar – any of various Spanish fortresses or palaces built by the Moors
battlement, crenelation, crenellation – a rampart built around the top of a castle with regular gaps for firing arrows or guns
defensive structure, defence, defense – a structure used to defend against attack; “the artillery battered down the defenses”
martello tower – a circular masonry fort for coastal defence
presidio – a fortress established in the southwestern United States by the Spanish in order to protect their missions and other holdings; “Tucson was first settled as a walled presidio”
sconce – a small fort or earthwork defending a ford, pass, or castle gate
Verb 1. fort – gather in, or as if in, a fort, as for protection or defense
foregather, forgather, gather, assemble, meet – collect in one place; “We assembled in the church basement”; “Let’s gather in the dining room”
2. fort – enclose by or as if by a fortification
inclose, shut in, close in, enclose – surround completely; “Darkness enclosed him”; “They closed in the porch with a fence”
trench – fortify by surrounding with trenches; “He trenched his military camp”
embattle – fortify by furnishing with battlements for defense; “an embattled castle”
3. fort – station (troops) in a fort
station, post, send, place – assign to a station
Permanent post as opposed to a camp, which is a temporary installation.
Land area within which harbor defense units are located.
A defensive work, exclusively military in nature, that is strengthened for protection against enemy attack and commonly incorporates a series of bastions (i.e., projections from the outer wall of the fort) to defend the adjacent perimeter; usually occupied by troops. See bastion, battlement, breastwork, casemate, embrasure, loophole, rampart.
a large fortified structure, either open (field) or enclosed (permanent).
Forts were first constructed in the 18th century, initially as separate fortifications outside a fortress wall and later, from the 18th to early 20th centuries, as part of a fortress or a fortified field position. Open forts assumed a variety of forms; they occupied an area of 4–5 hectares and were adapted to all-around defense. One or two earthen banks were erected around the perimeter, which measured about 1,000 m; the banks were protected by ditches and other obstacles, and 20–50 artillery pieces were placed behind the banks. The inside of the wall was equipped as a fire position. For purposes of defense, a garrison of two to four rifle companies was assigned to a fort and stationed in shelters, in addition to artillery crews.
Permanent forts were built of stone, concrete, armor, or other material. Initially, in the 18th century, they took the form of multilevel stone towers, armed with many guns. In the 19th century, forts were designed according to the bastion system; French forts had four or five bastions, each with 40–50 artillery pieces. Later, the caponier system was developed; in Germany, for example, forts were constructed with 20–30 artillery pieces, two flanking caponiers, and one central redoubt caponier.
As new types of fortifications came into use after World War I, such as defensive complexes and strongpoints, the fort lost its importance as an individual entity and henceforth was used only as part of a fortified area.