The Roman invasions of what is now Scotland was a continuation of their conquest of what became England and was conducted while the bulk of the Roman World was at peace enabling resources to be safely directed to the conquest of a peripheral area like Scotland. These attacks and invasions began around 80 AD and culminated in the full-scale invasion by the Emperor Septimius Severus (d. 211 AD). These invasions had a profound effect on what is now Scotland, then called Caledonia by the Romans. Chief amongst these effects was to cause the Celtic tribes above the Forth-Clyde line to increasingly coalesce in an effort to mount a more effective defence against the attacking Romans. This lead to a more hierarchically structured society designed to combat and defeat the Roman forces who from around 300 AD onwards increasingly referred to these people’s as ‘Picti’ or the painted or tattooed people. Below the Forth-Clyde line the tribes tended to cooperate with Rome and became allies or ‘foederati’ of the Roman people. Again this had profound consequences as culturally and socially those tribes adopted Roman customs which increasingly differentiated them from the tribes further north. This was particularly true of the Votadini of the south-east of Scotland who began to change significantly from those tribes beyond the Forth-Clyde line through the subsequent centuries. In particular after the adoption of Christianity by the Roman Empire in the later fourth century. From the year 300 AD onwards the balance of power increasingly shifted away from Rome forcing the Roman forces increasingly on to the defensive. Meanwhile the processes provoked and accelerated by the Roman interventions continued apace with the increased centralisation of these Celtic tribes continuing after Rome’s departure during the course of the early fifth century AD.