73), and at first sight more defensible than Hadrian's Wall, the additional area that it enclosed within the Empire was barren, with land use for grazing already in decay. This meant that supply lines to the wall were strained enough such as the costs for maintaining the additional territory outweighed the benefits of doing so. Also, in the absence of urban development and the ensuing Romanization process, the rear of the wall could not be lastingly pacified. It has been therefore speculated that the invasion of Lowland Scotland and the building of the wall had to do mostly with internal politics, that is, offering Antoninus an opportunity to gain some modicum of necessary military prestige at the start of his reign. Actually, the campaign in Britannia was followed by an Imperial salutation, that is, by Antoninus formally taking for the second (and last) time the title of Imperator in 142. The fact that around the same time coins were struck announcing a victory in Britain points to Antoninus' need to publicize his achievements. The orator Fronto was later to say that, although Antoninus bestowed the direction of the British campaign to others, he should be regarded as the helmsman who directed the voyage, whose glory, therefore, belonged to him. That this quest for some military achievement responded to an actual need is proved by the fact that, although generally peaceful, Antoninus' reign was not free from attempts at usurpation: Historia Augusta mentions two, made by the senators Cornelius Priscianus ("for disturbing the peace of Spain"; Priscianus had also been Lollius Urbicus' successor as governor of Britain) and Atilius Rufius Titianus (possibly a troublemaker already exiled under Hadrian). Both attempts are confirmed by the Fasti Ostienses as well as by the erasing of Priscianus' name from an inscription. In both cases, Antoninus was not in formal charge of the ensuing repression: Priscianus committed suicide and Titianus was found guilty by the Senate, with Antoninus abstaining from sequestering their families' properties. There were also some troubles in Dacia Inferior which required the granting of additional powers to the procurator governor and the dispatch of additional soldiers to the province. On the northern Black Sea coast, the Greek city of Olbia was held against the Scythians. Also during his reign the governor of Upper Germany, probably Caius Popillius Carus Pedo, built new fortifications in the Agri Decumates, advancing the Limes Germanicus fifteen miles