Fortifications are military constructions, or buildings, designed for the defense of territories in warfare and also used to solidify rule in a region during peace time. For many thousands of years, humans have constructed defensive works in a variety of increasingly complex designs. The term is derived from the Latin fortis ("strong") and facere ("to make").
From very early history to modern times, walls 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 construction mainly served the purpose of a watch tower, to guard certain roads, passes, and lands that might threaten the kingdom. 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 "castramentation" since the time of the Roman legions.
