Profile - Offa’s Dyke

The so-called “Dark Ages” that followed the fall of the Roman Empire in the west are no longer considered so “dark” as they were made out to be during the Renaissance and the Enlightenment. Indeed, there were quite a number of bright spots, among them the Anglo-Saxon Kingdom of Mercia, in what are now the Midlands of England.

Mercia emerged around A.D. 585 from the chaotic period that followed the collapse of Roman rule and the invasions of the Angles, the Saxons, and the Jutes during the fifth century. It grew rapidly under the leadership of a line of notable kings. The greatest of these was Offa.

Offa ascended the throne in 757, after defeating Beornraed, a distant cousin who had usurped the throne by murdering their mutual cousin King Æthelbald (716-757). Offa’s long reign (he died in 796) was characterized by several notable accomplishments, including the conquest of most of central England, the forging of strong ties with the Church, the chartering of towns and monasteries, and the establishment of a systematic law code. He also applied himself to one of the most notable engineering feats in western Europe since the fall of Rome, the construction of what is known as “Offa's Dyke,” a defensive barrier intended to serve as an obstacle to Welch raids into his kingdom.

Offa’s Duke runs along what is roughly the modern border between England and Wales, from Prestatyn, near Chepstow on the River Wye in the south, to the coast of North Wales. The dyke is 176 miles long, nearly twice that of the combined lengths of Hadrian's Wall (c. 75 miles) and the Antonine Wall (c. 37 miles). Like the two Roman walls, Offa’s Dyke follows high ground (thereby providing some impressive views of the countryside), and wherever possible takes advantage of natural barriers such as rivers and mountains, supplemented by about 80 miles of artificial barriers where no natural ones existed. Unlike Hadrian’s Wall, which is built of stone, much of Offa’s Dyke is made of earth, like the Antonine Wall. The dyke has a six-foot deep ditch on the Welch side, behind which runs an earthen bank up to 25 feet in height, along the top of which it there seems to have been a wooden palisade, occasionally supplemented by a stone wall. As a result, when it was new the dyke would have stood well over 30 feet high and about 60 feet wide, easily comparable to Hadrian’s Wall. It was built entirely using simple hand tools, which demonstrates an enormous organizational ability; the work required literally thousands of laborers, who had to be recruited, moved, fed, supplied with materials and tools, and protected, suggesting a great deal more organizational and logistical ability than is customarily ascribed to the Dark Ages. The scale of the effort suggests that it was one even the Romans would have been proud of.

Although apparently normally unmanned, Offa’s Dyke seems to have been moderately effective at hampering Welch raids into central England. Its presence meant that raiders would have had to waste time getting across the dyke, which would have permitted the Mercians time to gather forces, and even if the Mercians were late in arriving, they would have been able to attack the raiders when they tried to recross it. Another important result of building the dyke was that Offa defined the border between England and Wales. According to an old tradition, "it was customary for the English to cut off the ears of every Welshman who was found to the east of the dyke, and for the Welsh to hang every Englishman whom they found to the west of it."

Over the centuries the dyke deteriorated through the forces of nature and the works of men. Today the it is a major tourist attraction, and there is a hiking path along its full length. The remains of the dyke are protected by the British National Trust, and portions of the ditch and the embankment up to 10 feet high can still be seen, as well as some restored sections.