As the stronghold of a major tribe in the south-east, Camulodunum held strategic importance. A Roman legionary fortress or "castrum", the first permanent legionary fortress to be built in Britain, was established within the confines of Camulodunon (which was latinised as "Camulodunum") following the successful invasion in AD 43, and was home to the Twentieth Legion. A smaller fort was built against the Iron Age earthworks close to the Gosbecks high-status farmstead, and was home to the Ala Primae Thracum ("First Wing of Thracians", a cavalry regiment) and the Cohors Primae Vangionum ("First Cohort of Vangiones", a mixed cavalry-infantry unit from Gaul).