Governor of Britannia, was ordered by Antoninus Pius to march north of Hadrian's Wall to conquer the Caledonian Lowlands which were settled by the Otadini, Selgovae, Damnonii and the Novantae, and to push the frontier further north. Lollius Urbicus moved three legions into position initially establishing his supply routes from Coria and Bremenium and moved three legions, the Legio II Augusta from Caerleon, the Legio VI Victrix from Eboracum, and the Legio XX Valeria Victrix from Deva Victrix into the theatre between 139 and 140 AD, and thereafter moved his army, a force of at least 16,500 men, north of Hadrian's Wall. The Selgovae, having settled in the regions of present-day Kirkcudbrightshire and Dumfriesshire immediately northwest of Hadrian's Wall, were amongst the first of the Caledonian tribes to face Lollius Urbicus's legions together with the Otadini. The Romans, who were well versed in warfare on hilly terrain since their founding, moved quickly to occupy strategic points and high ground, some of which had already been fortified by the Caledonians with hill forts. One such was Burnswark Hill which was strategically located commanding the western route north further into Caledonia and where significant evidence of the battle has been found. By 142 the Romans had pacified the entire area and had successfully moved the frontier north to the River Clyde-River Forth area when the Antonine Wall was constructed. After two decades this was abandoned in 162 and only subsequently re-occupied on an occasional basis. Meanwhile, the Romans retreated to the earlier and stronger Hadrian's Wall. Roman troops, however, penetrated far into the north of modern Scotland several more times. Indeed, there is a greater density of Roman marching camps in Scotland than anywhere else in Europe as a result of at least four major attempts to subdue the area. 3rd and 4th centuries The most notable later expedition was in 209 when the emperor Septimius Severus, claiming to be provoked by the belligerence of the Maeatae tribe, campaigned against the Caledonian Confederacy, a coalition of Brittonic Pictish tribes of the north of Britain. He used the three legions of the British garrison (augmented by the recently formed 2nd Parthica legion), 9000 imperial guards with cavalry support, and numerous auxiliaries supplied from the sea by the British fleet, the Rhine fleet and two fleets transferred from the Danube for the purpose. According to Dio Cassius, he inflicted genocidal depredations on the natives