Caesar’s Rhine Bridge
Obviously, there are gaps in our knowledge of Roman construction techniques and tools because we lack either written or physical evidence of these. Non-permanent materials have eroded away over two millennia and their characteristics elude us. Great structures like Hadrian’s Wall survive because of the use of stone or concrete.
There is, however, one clear example of a non-permanent structure which we know a lot about – Caesar’s first bridge over the Rhine. We know the story because Caesar tells us in volume four of The Conquest of Gaul. But construction techniques are only part of the story. Caesar built this bridge to show the Germans they were never safe from him because he had the skills to cross the river and attack them.
In 55 B.C, the German tribes Usipetes and Tenctheri crossed the Rhine to the Roman occupied west bank and plundered corn they found there. Crossing back over, they joined forces with the Sugambri tribe. When Caesar sent an embassy to the Sugambri and asked that the culprits be returned to him, the response was that the Rhine was the limit of Roman authority. Simultaneously, the Ubii tribe, an ally of Rome, asked for help against the Suebi tribe who were harassing them.
Caesar, deciding he had enough reasons to cross the Rhine, planned an expedition to attack the Sugambri.