A longstanding debate among ancient historians and students of Roman frontiers concerns the reality and effective reach of Roman imperial policy. Certainly when new military commitments were involved, the slowness of supply and information meant that major moves had to be planned well in advance. This paper focuses on the provincialisation of Britain and Thrace in a.d. 43 and c. 45. The dating evidence provided by tree rings, coins and milestones suggests that logistic preparation for the invasion of Britain started at least two years before the event. This pattern, of a newly installed Emperor immediately initiating a campaign on the northern frontiers, allowing two years for logistic preparation, is seen no fewer than seven times between Caligula and Caracalla.
