Fort

A fortification is a

military

construction

or

building

designed for the defense of territories in

war

fare, and is also used to establish rule in a region during peacetime. The term is derived from

Latin

''fortis'' ("strong") and ''facere'' ("to make").

From very early history to modern times,

defensive wall

s have often been necessary for cities to survive in an ever-changing world of invasion and conquest. Some settlements in the

Indus Valley Civilization

were the first small cities to be fortified. In ancient Greece, large stone walls had been built in Mycenaean Greece, such as the ancient site of

Mycenae

(famous for the huge stone blocks of its 'cyclopean' walls). A Greek '' phrourion'' was a fortified collection of buildings used as a military

garrison

, and is the equivalent of the Roman

castellum

or

English

fortress. These constructions mainly served the purpose of a watch tower, to guard certain roads, passes, and borders. Though smaller than a real fortress, they acted as a border guard rather than a real strongpoint to watch and maintain the border.

The art of setting out a military camp or constructing a fortification traditionally has been called "

castra

metation" since the time of the

Roman legion

s. Fortification is usually divided into two branches: permanent fortification and field fortification. There is also an intermediate branch known as semi-permanent fortification.

Castle

s are fortifications which are regarded as being distinct from the generic fort or fortress in that they are a residence of a

monarch

or noble and command a specific defensive territory.

Roman forts

and hill forts were the main antecedents of castles in

Europe

, which emerged in the 9th century in the Carolingian Empire. The Early Middle Ages saw the creation of some towns built around castles.

Medieval-style fortifications were largely made obsolete by the arrival of

cannon

s in the 14th century. Fortifications in the age of black powder evolved into much lower structures with greater use of ditches and earth ramparts that would absorb and disperse the energy of cannon fire. Walls exposed to direct cannon fire were very vulnerable, so the walls were sunk into ditches fronted by earth slopes to improve protection.

The arrival of explosive shells in the 19th century led to yet another stage in the evolution of fortification. Star forts did not fare well against the effects of high explosive, and the intricate arrangements of bastions, flanking batteries and the carefully constructed lines of fire for the defending cannon could be rapidly disrupted by explosive shells.

Steel

-and-

concrete

fortifications were common during the 19th and early 20th centuries. The advances in modern warfare since

World War I

have made large-scale fortifications

obsolete

in most situations.

Nomenclature

Many United States Army installations are known as ''forts'', although they are not always fortified. Indeed, during the pioneering era of North America, many outposts on the frontiers, even non-military outposts, were referred to generically as ''forts''. Larger military installations may be called ''fortresses''; smaller ones were once known as ''fortalices''. The word ''fortification'' can also refer to the practice of improving an area's defense with defensive works. City

walls

are fortifications but are not necessarily called ''fortresses''.

The art of setting out a military camp or constructing a fortification traditionally has been called ''

castra

metation'' since the time of the

Roman legion

s. The art/science of laying

siege

to a fortification and of destroying it is commonly called ''siegecraft'' or ''siege warfare'' and is formally known as '' poliorcetics''. In some texts this latter term also applies to the art of building a fortification.

Fortification is usually divided into two branches: permanent fortification and field fortification. Permanent fortifications are erected at leisure, with all the resources that a state can supply of constructive and

mechanical

skill, and are built of enduring materials. Field fortifications—for example breastworks—and often known as ''fieldworks'' or ''earthworks'', are extemporized by troops in the field, perhaps assisted by such local labour and tools as may be procurable and with materials that do not require much preparation, such as

earth

, brushwood and light

timber

, or sandbags (see sangar). An example of field fortification was the construction of

Fort Necessity

by George Washington in 1754.

There is also an intermediate branch known as ''semi-permanent fortification''. This is employed when in the course of a campaign it becomes desirable to protect some locality with the best imitation of permanent defences that can be made in a short time, ample resources and skilled civilian labour being available. An example of this is the construction of Roman forts in England and in other Roman territories where camps were set up with the intention of staying for some time, but not permanently.

Castle

s are fortifications which are regarded as being distinct from the generic fort or fortress in that it describes a residence of a

monarch

or noble and commands a specific defensive territory. An example of this is the massive medieval castle of

Carcassonne

.

History

Neolithic Europe

From very early history to modern times,

walls

have been a necessity for many cities. In

Bulgaria

, near the town of Provadia a walled fortified settlement today called

Solnitsata

starting from 4700 BC had a diameter of about 300 feet (100 meters), was home to 350 people living in two-storey houses, and was encircled by a fortified wall. The huge walls around the settlement, which were built very tall and with stone blocks which are 6 feet (2 meters) high and 4.5 feet (1.5 meters) thick, make it one of the earliest walled settlements in Europe but it is younger than the walled town of Sesklo in

Greece

from 6800 BC. Uruk in ancient

Sumer

(

Mesopotamia

) is one of the world's oldest known walled cities. The Ancient Egyptians also built fortresses on the frontiers of the

Nile Valley

to protect against invaders from neighbouring territories, as well as circle-shaped mud brick walls around their cities. Many of the fortifications of the ancient world were built with mud brick, often leaving them no more than mounds of dirt for today's archaeologists.

A massive prehistoric stone wall surrounded the ancient temple of

Ness of Brodgar

3200 BC in

Scotland

. Named the "Great Wall of Brodgar" it was four metres thick and four metres tall. The wall had some symbolic or ritualistic function. The Assyrians deployed large labour forces to build new palaces, temples and defensive walls.

Neolithic Indus Valley

Some settlements in the

Indus Valley Civilization

were also fortified. By about 3500 BC, hundreds of small farming villages dotted the

Indus

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