Roman Conquest of Ireland (Hibernia Unanimis)

The Roman Conquest of Ireland was a gradual process, beginning effectively in AD 83 under the command of Gnaeus Julius Agricola during the reign of Emperor Domitian. The invasion followed a similar path as that of the conquest of Britain, establishing client states without direct military occupation in many cases. Ireland had experienced frequent trade and contact with the Romans since their settlement of Britain, and by the late first century Ireland was seen as a potential target to protect Roman settlements and trade missions in the region.

Agricola’s invasion would successfully conquer a small area in the east, as well as reinstate an exiled high king named Túathal Techtmar, who had been given refuge by Agricola. Ireland was de jure under Roman rule indirectly, however the high king only managed to directly control land in the center of Ireland, known collectively as Meath.

Preparations
Beginning in 82 AD, proconsul Gnaeus Julius Agricola began began preparing forces in northern England for an invasion across the Irish Sea, planning to re-instate Túathal Techtmar, an exiled king and son of the former king Fíachu Finnolach, who was previously deposed. According to Tacitus the Roman army consisted of one legion from Britannia, namely the Legio XX Valeria Victrix, under the command of Agricola, supported by large number of British auxiliaries. The Roman army numbers at least 8,000 auxiliaries, including four cohorts of Batavians and two cohorts of Tungrian swordsmen, 3,000 cavalry, and 17,000 to 30,000 overall. Likewise, with support from the Romans, Túathal Techtmar raised a large army of Irish auxiliaries and allies to join him in his cause. The Legio II Augusta was transferred from southern Britannia to the north to secure the border with the Caledonians. Agricola seemed confident in the security along the border, with this legion fortifying a series of fortifications constructed by Agricola and his predecessors.