Construction of Hadrian’s Wall began in 122 C.E., shortly before the Emperor Hadrian visited Britain as part of his numerous tours of the Empire’s frontiers. The wall was intended to help consolidate Hadrian’s Empire and secure its vast borders, which had proven a difficult task all across the Empire. This reflected Hadrian’s overall goal of preserving the Roman Empire, as opposed to expanding it, as his predecessor Trajan had. While in other areas of the Roman frontier a system of forts and outposts allowed the Romans to patrol and monitor their relatively open borders, in Britain the nature of the island allowed the Romans to construct a continuous barrier, which worked in conjunction with the usual system of frontier forts and outposts.
The Wall in the North, which exists within Martin’s fantasy universe, was constructed thousands of years prior to the events of A Song of Ice and Fire, and consequently far less is known of its construction and origins. Supposedly incorporating magical elements into the erection of the massive ice wall, this fortification nonetheless served a purpose similar to that of Hadrian’s Wall: to establish a secure border which could ease the burden of frontier defence. The enemy that the First Men aimed to keep out were not unruly tribes, but instead were a supernatural force of undead beings called the Others. However by the time of the events of A Song of Ice and Fire, the Others are thought to be extinct, as none have been seen for millennia. Thus, the Wall and its garrison, the men of the Night’s Watch, have grown weaker as the looming threat of the Others has decreased, as many people in the Seven Kingdoms believe the only threat North of the Wall is the Wildling tribes.
 David J. Breeze, The Frontiers of Imperial Rome (South Yorkshire: Pen & Sword Books Ltd., 2011), 144.
 George R.R. Martin, The World of Ice and Fire (New York: Bantam Books Ltd., 2014), 474.
 Ibid., 476.