Brochs, duns and forts in early Celtic Scotland

Sunday, December 25, 2016

by Angus Konstam
The background
When the Romans came to Scotland in AD 80, they knew little or nothing about the Celtic tribes who lived in the region. Faced with invasion, the tribesmen of the lowlands either submitted to Roman occupation or withdrew to what they thought was the safety of their hilltop forts. This proved a costly mistake, as the two largest forts in the area fell to the might of the Roman army and its siege artillery. The tribes who resisted (known by the Romans as the Selgovae and the Novantae) were brought to their knees by the end of the year, and the Roman Governor Agricola consolidated his northern frontier along the line of the Forth and Clyde rivers. The area was completely pacified by the start of AD 82. So much for the defensive protection of the lowland hillforts. Further north a fresh challenge awaited Agricola, as he planned to lead his armies into eastern and north-eastern Scotland, beyond the Firth of Forth. These Celtic tribesmen had used their fortified bases in what is now Stirlingshire to harry the Romans, and Agricola had had enough. In AD 83 he launched his legions in an expedition of conquest, cornering the local ‘Caledonian’ tribesmen in battle at Mons Graupius (84) and inflicting a decisive defeat on his opponents. During the advance his flanks were secured by a series of Roman auxiliary forts designed to prevent Caledonian movement out of the Highlands. His fleet sailed north as far as Orkney, forcing the submission of the coastal communities they encountered.
Although the Roman tide receded due to commitments elsewhere, the threat of punitive attacks against the Caledonian tribes continued, forcing the local Celts to maintain strong defensive positions and to ensure their near-constant readiness for war.

The Roman defensive line along the Forth–Clyde line was abandoned around AD 100, and the frontier was re-established between the River Tyne and the Solway Firth, a position which was defended during the reign of the Emperor Hadrian (AD 117–138). The Romans returned north for a time during the reign of the Emperor Antonius Pius (AD 138–161), and the Antonine Wall was built along the old Forth–Clyde line, before it too was abandoned after the death of the Emperor. From that point on Hadrian’s Wall marked the northernmost frontier of the Roman empire. Although the tribes immediately to the north of the wall were relatively peaceful, those further north were more hostile. At the start of the 3rd century AD the Emperor Septimus Severus (AD 193–211) led punitive expeditions against the Caledonians, as did the Emperor Constantius I Chlorus (AD 305–306) a century later. It was during this last expedition that we first hear of the Caledonians being referred to as the ‘Picts’, or painted people. Historians generally take this date as the mark that divides the era of the Picts from that of their Caledonian forebears, and provides a convenient finishing point for our study.

In early Celtic Scotland, there were three main types of fortifications in use during this period: the brochs, the duns and the hillforts.

Towers in the north: the brochs
The Broch of Gurness stands on the shore of a stunningly beautiful bay and sound in Orkney. It was built at some point between 500 and 200 BC, and the broch itself formed part of a defensive site that included a village and a series of encircling ramparts and ditches. The brochs of Iron Age Scotland were a virtually unique solution to the defensive requirements of their builders. Spectacular even in ruin, these structures often combined the functions of a defensive retreat with that of a communal focal point. They protected the local people from petty bandits, raiding war parties and on occasion, from full-scale invasions. As such they often formed the nucleus of small communities, or were located close to existing settlements. This means that any true study of them as fortifications needs to be combined with a look at the communities they served, and the people who built them. From there we can look at the fortifications which succeeded them, and which provided defensive strongpoints for the Picts, who inherited the land from the Iron Age broch-builders.

A broch was an imposing circular fortification built using drystone walling. This meant that no mortar was used, but the irregularly shaped stones were chosen so that they fitted roughly together. They were tall, grim, windowless structures, containing a passage within the walls which eventually led to an upper rampart. The only entrance was a small, easily-defensible doorway at ground level. Two walls were separated by passageways, stairs and galleries, which eventually led up through the walls to the circular upper parapet, where the defenders could rain missiles down on the heads of their attackers. While the Broch of Gurness is considered an early example of the genre, the Broch of Mousa in Shetland is probably the most intact example of a later (and more classical) broch structure. Precursors of the earliest brochs were probably the strong circular houses whose ruins are located in the same geographical area as the brochs.

Almost all brochs are located in the north and west of Scotland in Caithness, Orkney, Shetland and Skye, while a few others were built further south. The majority of them are concentrated in Orkney, Shetland and Caithness. Dating evidence suggests that most were built between the start of the 1st century BC, and the late 1st century AD, although this has been questioned due to the equivocal dating material so far discovered. Further evidence suggests that ‘proto-brochs’ or precursors to the classical broch structure could have been built as early as the 6th century BC, while we know that some remained in use until at least the early 3rd century AD, if not later. Although we know a lot about the structures themselves, and we can analyse their defensive qualities, we know very little about who exactly built them, and why. Obviously numerous theories have been proposed, and it was only recently that archaeologists reached a general consensus on what may have happened.

Clearly, they were designed for defence. The Broch of Mousa alone stands to a height of some 13 metres (40 feet), and would have been a proof against all but the most determined assault, unless the attacker had Roman-style siege artillery. The low narrow entranceway made it difficult to batter down the door, and the walls of Mousa were too high for ladders. The hollow interior was probably roofed over, and was large enough to house livestock, provisions and people until the threat had passed. We know little about who the threatening attackers might be, but Celtic, Roman or German raiding parties might have come to these areas in search of slaves. Although not impregnable, smaller brochs would have guaranteed that an attack against them would have been costly, and thus they acted as a form of deterrent against any potential aggressor.

Until comparatively recently, brochs were sometimes referred to as ‘Pictish towers’, or even associated with the Norsemen (vikings). While these links have been disproved, the terms indicate a general lack of understanding of the brochs and the broch builders. We know a certain amount about the late prehistoric people who lived in what is now Scotland from their archaeological legacy. They were not Scots, as that political entity post-dated the broch builders by a millennium, but we have no alternative name to identify them by, as no written records survive from this culture and period. The term ‘Celtic’ has been widely used to describe all the iron age people of this period who inhabited most of Europe, including Scotland, but some archaeologists baulk at using such a widely applied appellation. As for the term ‘Pictish’, their time came later, and the Picts have usually been identified with the inhabitants of north-east and east central Scotland from the early 4th century, when the name first appeared in Roman written records. The broch builders had been long gone by then, and while the Picts may well have been the descendants of these broch builders, archaeological information is unable to prove a clear descent from one group to the other. Various theories have been proposed, including ones where the Picts reached Scotland from overseas, and similarly that the broch people were somehow different from the pre-Celtic people who inhabited the rest of Scotland.

It is probably true that the pre-Celtic people of Scotland intermingled with later waves of Celtic migrants, but there is no direct Celtic broch building tradition. It has been suggested that while the rest of Scotland was overrun by the Celts, the broch builders retained their independence, and fortified their settlements. Whoever built them, their appearance coincided with the arrival of the Celts, and their disuse began following the arrival of the Romans in Scotland. Some archaeologists have given the broch builders the clumsy appellation of proto-Picts, but this does the earlier people a disservice. The broch builders displayed certain qualities which were absent elsewhere in the Pictish homeland (which included Orkney and Shetland), so although there are many theories, there are few answers to the mystery of who these enigmatic people were. It is possible that by the time the Pictish era, the local population had effectively become as Celtic as the rest of Scotland. Certainly we know that most brochs were abandoned at some point during the 3rd century AD, which is close enough to the appearance of the Picts as a distinctive people to suggest some link between the two dates.

Blockhouses in the west: the duns
The term ‘dun’ is used to identify a particular type of small fort which was built extensively all across south-western and western Scotland, with the greatest concentration found in Argyll. These circular or oval dry-stone structures were similar to brochs, but were much smaller. While some were built on flat ground, most were constructed on rocky outcrops or natural defensive positions to enhance their defensive properties. Their walls were usually built using two thick dry-stone walls, with a solid core of rubble used as infill between them. Some used timber to lace the structures together (as was the case with the first hillforts), but most had a smooth outer face, devoid of timber reinforcements. In some examples the wall was reinforced at the base to allow the construction of higher or heavier structures. Like the brochs, the entrance was small and protected by chambers to discourage battering attempts. A particularly impressive example (the Dun of Leccamore, on Luig) even boasts an internal stairway, and other design features suggest some form of correlation between the broch builders and the defensive properties of these smaller dun structures.

While some earlier timber-laced duns have been dated to the 6th or 5th century BC, the majority appear to have been built during the period after the Romans came to Scotland, during the 2nd and 3rd centuries AD. Some show evidence of occupation, abandonment and re-occupation, suggesting they were used when the situation warranted it, and in more peaceful times they may have been abandoned for more spacious and convenient settlements nearby. They also show signs of a far longer occupation than the brochs to the north or the hillforts to the south and east. Dun Cuier on Barra was occupied until around AD 500, while Kildalloig in Argyll appears to have remained in use as late as the 8th century. Unlike the brochs or hillforts, most duns appear to have been little more than fortified homesteads or farms, but they remained a feature of the Scottish landscape for over a thousand years, and outlived both other forms of early Celtic fortification.

Strongholds in the south: the hillforts
Nobody knows how or exactly when the Celts reached Scotland. Towards the end of the Bronze Age (around 700 BC), these newcomers began to arrive, bringing the new technology of the Iron Age with them. These Celts also introduced a new feature to the Scottish landscape. Over the next eight centuries, hillforts would appear in various sizes, from small fortified farms to full-scale fortified hilltop townships. They provided refuge for the local Celtic communities who faced attacks and raids from their neighbours. While well-designed to protect the Celtic tribespeople from their own kind, they proved less effective against the Romans.

Although the early Bronze Age defensive ring at Meldon Bridge in Lothian is probably the earliest fortified site in Scotland, the first hilltop fortifications appeared around 600 BC or slightly earlier. These took the form of timber-laced fortified circles. In some cases the ramparts were fire damaged during their period of use, which allowed the sites to be carbon dated. While the dating range is wide most appear to have been actively built or expanded during the 6th century BC or later. These timber-laced structures continued to be built in Scotland until the coming of the Romans in the late 1st century AD, although the style of the fortifications became more elaborate with time. Timber-lacing was a technique used to stabilise both earthen ramparts, stone walls or rubble infill by laying horizontal wooden beams across the structure, binding it together. In other words, the timber provided a massive framework which was filled with stones and rubble, then faced with solid stone. A wooden walkway and palisade were then built on top of this defensive perimeter. Thick wooden gates protected the entrances to these hilltop enclosures.

Surviving examples such as the stone and earthen wall of the fortification at Abernethy in Perthshire (occupied during the 1st century BC) show the surviving slots in the walls where these beams were placed, and had rotted away. In cases where the forts were destroyed by fire (probably during an assault), fire damage caused by the burning timber has left its mark on the surviving stonework, which has sometimes been fused together. In rare instances, the remains of timber-lacing survives, such as at Kaimes Hill in Midlothian. Timber-laced forts were built throughout central and eastern Scotland and around the Moray Firth to the north, and this distribution matches that of early Celtic finds such as axe heads dating from the 7th century BC and later. This proves that the early Celtic people who occupied central and eastern Scotland relied on these types of fortifications for their protection.

The nature of these hillforts changed over time. In some cases, the original timber-laced structures were replaced or rebuilt in later periods. At Kaimes Hill a series of stone-faced ramparts replaced these earlier defences, and a series of ditches were dug around the perimeter to strengthen the position. One additional refinement was the setting of a ring of pointed stones around the outside of the wall, creating a disruptive obstacle which would hinder any attackers. The trouble with timber-lacing was that the timbers were difficult to replace once they rotted, or they could be destroyed by fire with relative ease. Archaeological evidence suggests that while timber-lacing continued to be used in Scotland during the early Celtic period, the weakness of the design was apparent to the builders. Consequently when the local Celtic tribes of lowland Scotland were faced with the prospect of Roman invasion in the late 1st century AD, many forts were strengthened and improved by the addition of all-stone walls and the digging of ditches outside the walls. In addition to their walls or earthen ramparts, most of these defensive positions were topped by wooden palisades.

These forts were almost exclusively built on hilltops to impove their defensive capabilities, and in many cases the walls enclosed some form of interior settlement. Of some 1,500 fortified sites in Scotland, the majority of these forts were located in lowland Scotland, below the Forth–Clyde line. This surprisingly high figure includes small fortified farmsteads and isolated stone structures from the same early Celtic period. As some of these were built over 700 years before the Romans appeared, it comes as no surprise that many had been abandoned for centuries by the 1st century AD, although a handful remained in continuous use throughout their history. Unlike the sprawling hillforts such as Maiden Castle in England, these Scottish fortifications were small, and probably only served small local communities. The two exceptions were Traprain Law and Eildon Hill, both of which were substantial defensive positions, and the latter containing over 300 roundhouses. This meant that in times of danger, an entire tribe could seek refuge within its walls. One of the problems with Scottish hillforts is the lack of available information about their history. We rarely know how long they were occupied or when, and what function they served apart from a defensive one. It does seem that at least at certain periods, the hillforts which enclosed settlements tended to be under continuous occupation when the Romans appeared.

Another variant of the hillfort was the promontory fort, which was found at various points along the east coast of Scotland, such as St. Abb’s Head, Dunnotar and Urquhart (the last was actually on the shores of Loch Ness, not the North Sea). All but the last were most probably established as fortified sites well before 300 AD, but all three were developed into major fortifications during the Pictish period, and the last two were actual Pictish fortifications. Similarly, the promontory at Burghead on the Moray Firth was developed as a Pictish stronghold. In all three sites, elements of the old hilltop fort designs were used, as the headland was cut off from the mainland by a series of defensive walls and ditches. Again, the Burghead fortification may have predated the start of the historic Pictish period, but the lack of hard dating evidence makes it impossible to say so with any certainty. Certainly the system of three lines of earth and rubble defences and intervening ditches is similar to that found in hilltop forts from 300 BC on, and we know the Picts added an inner citadel to the fortified point at Burghead. The spot was also a good anchorage, and it has been suggested that Burghead was used as a Pictish base from which maritime raids were launched down the coast into Roman Britain. Certainly there seems to be a legacy of construction methods which linked the known Pictish fortifications (Inverness, Dunadd, Dundurn, Dunottar, Dunkeld, Clunie, Scone, Inveralmond and Forteviot) to the earlier hilltop forts in the same area (Tayside, Moray and Grampian).


To sum up, although the Iron Age landscape of Scotland is littered with fortifications, these can be divided into three groups. The brochs of the northern and western isles are virtually unique, and their design displays a high level of architectural and military appreciation. To the south-west the duns were smaller counterparts, and less likely to be situated in coastal locations. These remained in use until well after the arrival of the Scots from Ireland, and outlasted all but a handful of coastal fortifications which were probably used by both the Celts and their Pictish descendants in eastern Scotland. As for the rash of hillforts in southern Scotland, the majority fell from use following the Roman invasion of the late 1st century AD. Despite this, their methods of construction were adapted for use by the Picts as well as the Scottish peoples who inhabited the southern lowlands when the Romans withdrew. Scotland is unique in that so many of its monuments are still extant, and have been saved from centuries of development. Although the region produced methods of early Celtic fortification that were unique, any study of these defensive sites helps us understand both the people who built them, and their Pictish or Scottish descendants.

Further Reading

Armit, Ian, Celtic Scotland, Historic Scotland Publication – Batsford Press, London, 1997
Breeze, David J., Roman Scotland, Historic Scotland Publication – Batsford Press, 1996
Ritchie, Anna, and Breeze, David, Invaders of Scotland, Historic Scotland Publication – HMSO, 1990
Ritchie, Graham and Anna, Scotland: Archaeology and Early History, Edinburgh University Press, 1991
Ritchie. J. N. G., Brochs of Scotland, Shire Publications, 1988
Sutherland, Elizabeth, In Search of the Picts, Constable and Co., 1994
Wagner, Paul, Warrior 50: PictishWarrior AD 297–849, Osprey, 2002


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