1. The Scotland England border had always been a conflict line but after the death of Alexander III, the stage was set for the Scottish wars of Independence when armies would regularly pass through the lands, taking what they needed or laying waste to what they did not. Settlers suffered abysmally and so they learned that to survive they had to be opportunistic and predatory. A culture evolved where people simply took what they needed from others.
2. The topography of the border landscape does not make for good arable farming. Combined with the hereditary tradition of splitting up land amongst children, it made little sense for settlers to do anything other than raise livestock on the open fields in order to survive. This presented opportunities for families to raid one another's animals, rounding them up using their knowledge of the land and their horsemanship skills.
3. Rules developed as time passed in order to curb the development of potentially murderous feuds (although this is not to say they didn't occur!) There were truce days, when disputes were resolved and there was also the right to pursuit which stated that a person who had been raided could conduct a counter raid within six days and not be prosecuted. The borders were also administered and patrolled by both English and Scottish sides. Reivers risked execution if caught but they were skilled horseman, who often raided alongside the sheriffs appointed to try and stop them!
4. Mobility was the main defence of the Reiver but they also carried an array of weaponry and light protective padded armour.
5. The legacy of the Reivers has often been a romantic one. Perhaps this is because their lifestyle conjures an image of a free life spent in mountain and forest landscapes. Sir Walter Scott was one of the many poets who seems to have thought so. It should be noted however, that during Tudor times the raids had got so bad that a proposal was considered to rebuild Hadrian's Wall. The Reivers heyday lasted until the reign of James VI. James ruthlessly dealt with the Reivers, hanging many without trial, dismantling the administration of the region, forcibly sending many to the plantation of Northern Ireland or North America and conscripting them into the Army. It is no coincidence that many of the infamous criminals of the American Wild West had Reivers family names!