Wall of Severus as the mid-5th century predating the 8th-century reign of the Saxon King Offa of Mercia by 300 years. Septimius Severus arrived in Caledonia in 208 after Picts began making a series of attacks and incursions since 197. During these military operations in Scotland, the Wall of Severus was reportedly built. Cassius Dio, a Roman historian who lived at the time of Severus, makes no direct mention to any new fortification but does allude to the existing Antonine and Hadrian Walls. Late Roman historians interchange the name Severan Wall with the Antonine Wall. Other historical writers like Bede - an 8th-century
Architecture of Scotland Trimontium, and a continuous fortification between the Firth of Forth and the Firth of Clyde known as the Antonine Wall, built in the second century AD. Beyond Roman influence, there is evidence of wheelhouses and underground souterrains. After the departure of the Romans there were a series of nucleated hill forts, often utilising major geographical features, as at Dunadd and Dunbarton. Castles arrived in Scotland with the introduction of feudalism in the twelfth century. Initially these were wooden motte-and-bailey constructions, but many were replaced by stone castles with a high curtain wall. In the late Middle Ages new castles were