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Military Masterpiece: Caesar’s Bridge Across the Rhine

Julius Caesar was, perhaps, the most consequential Roman to have ever lived. In the course of his long and eventful life, he became a powerful politician and general, won countless battles against overwhelming odds, conquered Gaul for the Roman state, started a civil war to destroy the Roman Republic and replace it with a dictatorship, killed tens of thousands of his fellow countrymen, and was then stabbed by a bunch of his colleagues so much that today we have an entire salad named after him. Maybe. I mean they named the pizza chain after him, so it’s probably a similar story.

Whatever the historical (or gastronomical) verdict on Caesar, it cannot be debated that he was a man who changed the course of Roman history, for better and for worse. Today, however, we are going to take a look at a microcosm of Caesar’s career, something that was ultimately overshadowed by the later events of his life. This is Caesar’s bridge across the Rhine.

A Decade in Gaul

The Gallic Wars were not one continuous conflict. Rather, it was an on-off state of war between the Gallic tribes of France and Belgium and Julius Caesar’s legions. Ostensibly, Caesar was in the area to aid tribes that were allied with Rome against tribes that were not. It wasn’t true, ultimately, but Caesar kept up the charade for quite a while. Early on in his campaigns, Caesar resolved to do something extraordinary, something that had never been done before: take a Roman army across the sea to an unknown and mythical land where it was said that gold and pearls lay openly on the ground, where the warm sun would shine every day and where the native people were famed for their kind and welcoming demeanor – a place we know today as Britain. You can just imagine Caesar’s disappointment on that one.

Jokes aside, at the time of Caesar’s military career, the island of Great Britain was more or less a mystery to the Roman world, and there was much speculation and many myths surrounding it; some people wondered if it even existed at all. Caesar was a big PR guy, and he decided that being the first Roman general on the island would instantly turn him into even more of a rockstar than he already was. At this time, Caesar had established himself as a powerful player in Gaul, acting as the de facto representative of the Roman Republic to the tribes in the area. As a side note here, don’t let the word “tribes” fool you; Gaul wasn’t some backwater, they had well developed industries and large cities on the scale of Roman towns. This was part of the reason why Caesar had sought to conquer the region for Rome, and why he was now inserting himself into Gallic politics.

Getting back on track, Caesar made several military moves against several Gallic tribes in the year 56 BCE, with the purpose of securing his position in Gaul so that he could make an expedition to Britain in the following year. But unfortunately for him, he was about to run into the same problem that Italians have been running into for decades: Germany.

A Distraction on the Rhine

One of the persistent themes in the early Gallic Wars is both Caesar’s and Gaul’s conflicts with Germanic tribes, on the other side of the Rhine river. Indeed, German-French rivalry runs so deep it goes all the way back to Roman times. More importantly for our purposes, it was about to mess up Caesar’s plans.

In the year 55 BCE, Caesar was finishing up his preparations to cross the English Channel when some Germanic tribes began to cross the Rhine, seeking both Rome’s protection and a new home in Gaul after being forced away from their old one in Germania. Caesar, having absolutely no chill, instead attacked them and drove them back across the Rhine. While we shouldn’t gloss over the fact that this is a real jerk move to pull on people who are just asking for your help, Caesar had his reasons.

First, he wanted Gaul to be stable for him to make his crossing to Britain, and he worried that conflict across the Rhine would lead to spillover in Gaul. Second, a sizeable number of Gallic tribes were not happy about Caesar’s presence in their home; he’d fought several of them in battle only last year. Caesar believed that if the situation became unstable, it would provide an opportunity for some of the more hostile tribes to attack him. By the way, Caesar was right to be worried about that, and the Gauls were right to be alarmed with Caesar’s presence. Third, Caesar needed to make his crossing early in the year, because the weather in the English Channel would make a crossing all but impossible in the later seasons. So there was a logic behind his moves, even though none of it really excuses the fact that he needlessly killed thousands of people who were not a threat. Whatever, it’s ancient times, everyone’s a jerk.

After his “military victory” against a bunch of civilians, Caesar concluded that if he didn’t act, the Germanic tribes on the other side of the Rhine were going to continue causing problems for him and the Gauls. He decided that in order to pacify the region and make his expedition to Britain a reality, he needed to make a show of force to the Germanic tribes and let them know that Rome could bring the fight to them whenever it wanted. To that end, he moved his army to the Rhine river and prepared to cross it into Germania. A Germanic tribe that was allied to Rome offered to ferry his army across, but Caesar had a big ego and said in response, “Go big or go home”. Well, actually he said that such a thing was not “consistent with his own dignity or that of the Roman people”. So y’know, close enough. He wasn’t going to use boats to cross the Rhine; no, he was going to build a bridge.

A Different Kind of Challenge

Caesar’s Rhine Bridge, by John Soane (1814)

The Rhine river is not a very friendly river to bridges. It’s one thousand feet across, thirty feet deep, and has powerful currents from the sheer volume of water moving through it. Already it’s going to be a challenge based on that, but this bridge also needs to support having 40,000 soldiers crossing it and, for the sake of speed, has to be made out of wood. To say that such a thing was going to be tough would be an understatement. Thankfully, Caesar was thoughtful enough to lay out in his commentaries on the Gallic Wars exactly how he created this bridge, sparing no details. And I must warn you, you’re about to hear the word “pile” a lot. Ready? Okay.

First, the Romans would take two piles, long columns of wood, in this case one and a half feet thick, and sharpen the bottom ends into stakes. They would then use large pile drivers to ram these piles into the bed of the river, with two feet of distance between them. After sinking each pile into the bed of the river, they fastened them together with wooden braces, and this made up one set of piles on the bridge, serving as a part of the foundation.

Interestingly, the piles were not driven in vertically like they would normally be for any other bridge, but rather they were driven in at an angle. On the upstream side of the foundation, the piles were angled in the direction of the current; on the downstream side, forty feet opposite, another set of piles were angled against the current. This gave the bridge a trapezoidal shape, and a good deal of structural integrity against the powerful Rhine currents.

Next, Caesar had each set of opposite piles joined together with a long beam of wood two feet thick. He then had timber laid perpendicularly across these beams along the length of the river, and then on top of that timber he had “laiths and hurdles” (read: a bunch of sticks) laid over them. Lastly, Caesar had a final set of piles driven into the river on the upstream side of the bridge. These piles were placed in front of the other piles to create a triangular shield, which served to further protect the bridge from currents, as well as blocking any debris or, in Caesar’s words, “vessels floated down the river by the barbarians for the purpose of destroying the work”.

So, a trapezoidal bridge, made up of double-piles braced together, beams laid across them, timber laid across that, sticks laid across that, and shielded with a final set of piles from any currents, debris, or Germans jealous that they’d just been out-engineered by an Italian. And all in all, it only took Caesar and his men ten days from start to finish. Take a moment to just appreciate how fast that is. Construction and infrastructure projects today are delayed all the time, and yet Caesar came along and built a working bridge across the Rhine in just ten days. That’s insanely fast.

In any event, with his bridge now completed and access to the other side of the river thus gained, Caesar left a garrison to protect the bridge from attack and proceeded to march his army into the German interior.

A Man of Many Firsts

Rather anticlimactically, Caesar’s march into Germany ultimately didn’t accomplish much; most of the nearby German tribes had already fled inland for safety. It did, however, give him the distinction of being the first Roman general to lead an army across the Rhine; Caesar, being the aforementioned PR man that he was, played that up to the public back in Rome.

After eighteen days, when Caesar decided he was satisfied burning down empty villages in Germany, he pulled his legions back across the Rhine and then ordered the bridge to be destroyed to deny the Germans from being able to use it. Which is a pretty alpha move, all things considered. “Yeah, I built a bridge across the Rhine in ten days, then I just knocked it down because I don’t even care, y’know?”

Whatever the case, Caesar would go on to lead his expedition to Britain, and in the following years would continue his nearly unparalleled military and political career through the Gallic Wars, the Roman Civil War, and the aforementioned getting a salad named after him. Probably. But when looking at the list of achievements in Caesar’s life, the Rhine bridge stands out all the more for its relative inconsequence. Think of it this way: if it had been any person other than Caesar who built this bridge, it would have been a life-defining accomplishment. Yet for Caesar, it was just another summer. We can’t all have lives like that, and in retrospect, maybe it’s better not to have salads named after us. Food for thought. Thanks for watching.

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