The Border Reivers were bands of horsemen, organised on clan or family lines, who terrorised the remote districts on both sides of the Anglo-Scottish border between the fourteenth and sixteenth centuries. The term 'reiver' means thief, and the reivers lived by stealing cattle, other livestock and goods from rival families. Often the raids would be made across the border, but equally as often attacks would be made for 'clan' rather than 'national' reasons, and confederations of groups, from both sides of the border, would co-operate against their mutual rivals. Reivers were also known as 'steel bonnets' and as 'moss troopers'.
The reivers operated in Northumberland and Cumberland in England, Dumfries and Galloway and Scottish Borders in Scotland, although larger raids often ventured further afield. These were upland areas, where livestock farming was of greater importance than arable, and cattle formed the most valuable movable good.
Society in the Borders was focussed very much on the family, and the writ of central government, from London or Edinburgh, was only loosely enforced. Both the English and Scottish monarchies attempted to strengthen their rule in the borders by dividing the border area into 'Marches', ruled by Wardens chosen from local gentry; often the effect of this was only to inflame local rivalries.