Limes Pannonicus

The Pannonian Limes (Latin: Limes Pannonicus, German: Pannonischer Limes) is that part of the old Roman fortified frontier known as the Danubian Limes that runs for approximately 420 kilometres from the Roman camp of Klosterneuburg in the Vienna Basin in Austria to the castrum in Belgrade (Singidunum) in present-day Serbia. The garrisons of these camps protected the Pannonian provinces against attacks from the north from the time of Augustus (31 BC-14 AD) to the beginning of the 5th century. In places this section of the Roman limes also crossed the river into the territory of the barbarians (Barbaricum).

The Danubian limes was one of the most turbulent regions in the European part of the Roman Empire and, during more than 400 years of Roman rule, Pannonia was one of its most important provinces, especially after the abandonment of Dacia Traiana in 271 AD, because from that point on, the pressure of migrating peoples on this section of the limes increased still further. The limes also had a great influence on the economic and cultural life of the civilian population because its hinterland was one of the main supply areas for the border troops and these in turn were the guarantors of the rapid Romanisation of the province.

The majority of the occupying forces were stationed in camps (castra), small forts (castella), watchtowers, burgi and fortified bridgeheads that were built at regular intervals along the riverbank. In an emergency, these units were reinforced by the legions which had their headquarters in four major military garrison towns. With its advance to the Danube, the Roman Empire became engaged in a long series of conflicts with trans-Danubian Germanic and Sarmatian barbarian and migrant peoples, that finally ended in the 5th century with the collapse of the Empire in the west.

...
Wikipedia