The Limits of the Empire
As Rome expanded out of Italy from the 2nd century BC, there was no force capable of stopping its legions. It’s also important to note that conquest wasn’t always a straight-forward military matter. Rome traded and talked with neighbouring peoples, often having client kings in place before the troops went in. And the Empire – civilised, peaceful, prosperous – was an attractive system to join.
Everything has limits though and Rome found its in the early 2nd century AD. The subsequent problems in enforcing central power and the eventual splitting of the Empire into as many as four parts suggests that this territory was already too much to manage successfully. Some historians argue that the limit was military, marking a boundary between cultures that fight on foot and the masters of cavalry warfare whom Rome could not defeat.
The Empire at its largest extent, at Trajan’s death in 117 AD.
Many of the Empire’s boundaries were natural. For example, in North Africa it was the northern edge of the Sahara. In Europe, the Rhine and Danube rivers provided stable eastern borders for long periods; in the Middle East it was the Euphrates.
The Last Outpost
The Romans also built great frontiers. These were called limes, the Latin word which is the root for our ‘limits’. They were considered the edge of defensible territory and Roman power, and there was an understanding that only exceptional circumstances justified going beyond them. Soldiers sometimes mutinied when they felt the limes were preventing them from doing their job, and were often rewarded with an expedition to sort out whichever uppity tribe had provoked them.
The nature of the defences varied from place to place. Hadrian’s Wall, marking the northern edge of the Empire in Britannia, was the most impressive, with its high stone walls and well-designed and built forts. In Germania, the limes started as an area of felled forest, like a fire break with wooden watch towers. A wooden fence was later added and more forts built. In Arabia, there was no barrier. An important road built by Trajan marked the boundary and forts were built at regular intervals and around the easiest invasion routes from the desert.
Even at their most imposing the limes could be a little porous. Trade was allowed, and people north of Hadrian’s Wall were being taxed to some extent. In fact, the borders of the Empire were commercial hotspots.
The Limes: Rome’s Imperial Borders
The best known and preserved limes are:
From the Solway Firth to Wallsend on the River Tyne in the north of the UK, this 117.5-km wall was 6 metres tall in places. A ditch protected the north of the wall while a road to the south helped troops get about quickly. Small mile castles were supplemented with major forts at larger intervals. It only took six years to build. The Antonine Wall further north wasn’t a manned frontier for long.
The Limes Germanicus
This line was built from 83 AD and stood firm until around 260 AD. They ran from the Rhine’s northern estuary to Regensburg on the Danube at their longest, a length of 568 km. Earthworks were supplemented with a palisade fence with walls being built later in parts. There were 60 major forts and 900 watchtowers along the Limes Germanicus, often in several layers where invaders could mass in large numbers.
The Limes Arabicus
This frontier was 1,500 km long, protecting the province of Arabia. Trajan built the Via Nova Traiana road along several hundred kilometres of its length. Large Forts were placed only at strategic danger points with smaller forts every 100 km or so.
The Limes Tripolitanus
More of a zone than a barrier, this limes defended important cities in Libya, first from the desert Garamantes tribe, who were persuaded that trading with Rome was better than fighting it, and then from nomadic raiders. The first fort was built in 75 AD. As the Limes grew they brought prosperity, with soldiers settling to farm and trade. The boundary survived into the Byzantine Era. Today, the remains of Roman fortifications are some of the best in the world.
—The Limes Alutanus marked the eastern European frontier of the Roman province of Dacia.
—The Limes Transalutanus was the lower-Danube frontier.
—Limes Moesiae ran through modern Serbia along the Danube to Moldavia.
—Limes Norici protected Noricum from the River Inn to the Danube in modern Austria.
—Limes Pannonicus was the boundary of the province of Pannonia in modern Austrian and Serbia.
The British and German limes are already part of a UNESCO World Heritage Site and more will be added in time.