Hillforts in Scotland

Hillforts in Scotland are earthworks, sometimes with wooden or stone enclosures, built on higher ground, which usually include a significant settlement. They were introduced into Scotland during the Bronze Age from around 1000 BCE. The largest group are from the Iron Age, with over 1000 hillforts, mostly below the Clyde-Forth line, most of which were abandoned during the period of Roman occupation of Britain. There are also large numbers of vitrified forts, which have been subjected to fire, many of which may date to this period. After Roman occupation in the early Middle Ages some hillforts were reoccupied and petty kingdoms were often ruled from smaller nucleated forts using defensible natural features, as at Edinburgh and Dunbarton.

Early studies
The first major study of Scottish hillforts was undertaken by General William Roy and published as The Military Antiquities of the Romans in Britain in 1793. However, Roy only recorded forts like Burnswark with a close relationship to Roman constructions or which he wrongly attributed to be Roman in origin. George Chalmers' (1742–1825) first volume of Caledonia (1807) contained an arbitrary list of forts, but recognised that defences at Burnswark were not just in anticipation of Roman invasion, but to defend against native threats. He also recognised some of the relationships between major and subordinate sites, and the importance of intervisiability between sites. The first serious field research was undertaken in the 1880s and 1890s by David Christison.

Classification
A. H. A. Hogg identified four types of hillfort: contour forts, promontory forts, cliff forts and ridge forts. Contour forts, where banks and ditches are moulded to the shape of the hill, are the dominant form in Scotland. Promontory forts, usually employing coastal features can also be found, such as the largest one in Scotland at the Mull of Galloway. Different types of defensive style occur throughout the Iron Age period, some of which may have been a response to Roman siege warfare. There are different combinations in the use of earth, stone or timber. Timber was frequently in-filled with stone or other materials. In continental Europe the timber is often arranged vertically, but in Scotland horizontal timbers were more common.

Bronze Age
Bronze working developed in Scotland from about 2000 BCE. As elsewhere in Europe, it was in this period that hillforts were first introduced to Scotland. They varied in size and form. Some had timber palisades and others ditches and ramparts. These included the occupation of Eildon hill near Melrose in the Scottish Borders, from around 1000 BCE, which accommodated several hundred houses on a fortified hilltop. Traprain Law in East Lothian, had a 20-acre enclosure, sectioned in two places west of the summit, made up of a coursed, stone wall with a rubble core. The function of these forts have been debated, with some stressing their military role and others their importance as symbolic centres of local society.

Iron Age
There is evidence for about 1,000 Iron Age hillforts in Scotland, most located below the Clyde-Forth line. The majority are circular, with a single palisade around an enclosure. They appear to have been largely abandoned in the Roman period, but some seem to have been reoccupied after their departure. There are also numerous vitrified forts, the walls of which have been subjected to fire, which may date to this period, but an accurate chronology has proven to be evasive. Extensive studies of such a fort at Finavon Hill near Forfar in Angus, suggests dates for the destruction of the site in either the last two centuries BCE, or the mid-first millennium CE.

Early Medieval
For the period after the departure of the Romans there is evidence of a series of new forts, some of which became the centres of competing kingdoms. These were often smaller "nucleated" constructions compared with those from the Iron Age, sometimes utilising major geographical features, as at Edinburgh, which was probably the main fortification of the Brythonic kingdom of the Gododdin and Dunbarton rock, who gave its Brythonic name of Alt Clut to the kingdom that dominated the Strathclyde region in the post-Roman period. All the northern British peoples utilised different forms of fort and the determining factors in construction were local terrain, building materials, and politico-military needs. The first identifiable king of the Picts, Bridei mac Maelchon (r. c. 550-84) had his base at the fort of Craig Phadrig near modern Inverness. The Gaelic overkingdom of Dál Riata was probably ruled from the fortress of Dunadd, now near Kilmartin in Argyll and Bute.