Overview
It is generally accepted that much of the earthwork can be attributed to Offa, King of Mercia from 757 to 796. Its structure is not that of a mutual boundary between the Mercians on the one side and the people of Powys on the other. The earthwork was dug with the displaced soil piled into a bank on the Mercian (eastern) side. Where the earthwork encounters hills, it passes to the west of them, constantly providing an open view from Mercia into Wales. The dyke may have been constructed as a defensive earthwork, as well as a political statement of power and intent.
Offa was one of the great rulers of Anglo-Saxon times, though his reign is often overlooked due to a limitation in source material. That he was able to raise a workforce and resources sufficient to construct such an earthwork as Offa's Dyke is testament to his power. It is likely that some form of 'service' system along the lines of corvée was used to construct the Dyke, with people from certain areas being required to build a certain length of the wall. This can be seen as additional to the normal services that had to be offered to kings. A document exists from around this period known as Tribal Hidage, which makes some assessment of how land was distributed in the 8th century. Though there is little evidence to associate the document with the Dyke, it is possible that both the Dyke and the document stem from a common practice.
Read more about this topic: Offa's Dyke