Caesar's Rhine bridges

[qarnos]

Casting a skeptical eye to history, what evidence exists that Caesar actually built bridges across the Rhine? The claims are quite extraordinary: That Caesar's army built a bridge across the Rhine in just 10 days using nothing more than local timber (which had to be cut down first).

Oh, BTW, he had the bridges dismantled afterwards so the "bad guys" couldn't use it, so you just have to take Caesar's word for it that he really built them.

I seems to be taken at face value by most historians that this actually happened. Given the fact Caesar wasn't exactly immune to exaggerating his accomplishments for political advantage, how can we be sure this ever really happened? Especially in 10 days! It just seems absurd.

I am more than happy to be proven wrong, because I am genuinely interested in finding out how we know this is true, but I can never really come up with anything beyond "someone said so".

 

[Jack by the hedge]

I thought the Romans transported engineering materials like timbers pre-cut to build standard structures. So is the historical claim that they built a bridge from scratch in 10 days using local materials or could they have taken 10 days constructing a bridge after spending considerably longer bringing up supplies of parts?

I only vaguely remember the story. Is there more to it than the basic claim they built a bridge in that time?

 

[qarnos]

or could they have taken 10 days constructing a bridge after spending considerably longer bringing up supplies of parts?

Every telling of the story I have heard/read is that it was from scratch in 10 days using local timber. This is what is always exclaimed to be the "extraordinary" (with no hint of skepticism) part of the story.

 

[Cosmic Yak]

The alternative is that Caesar got his army to swim across the Rhine. I find that significantly less plausible.

 

[theprestige]

The alternative is that Caesar got his army to swim across the Rhine. I find that significantly less plausible.

More plausible would be that he did nothing. His visits across the Rhine were brief, and had no significant result.

He may have also used boats, which apparently were available.

 

[kookbreaker]

Every telling of the story I have heard/read is that it was from scratch in 10 days using local timber. This is what is always exclaimed to be the "extraordinary" (with no hint of skepticism) part of the story.

He did have some 8 legions under his command. That’s at least 24,000 able bodied laborers. Even accounting for the need for patrols, foraging, it doesn’t seem that odd. He could have the heavy labor working round the clock once the engineers set things in place.

 

[Hellbound]

Doesn’t sound too far-fetched to me. I’m not familiar with the details of the historical story, but nothing in the time frame suggests impossibility.

First, keep in mind that a temporary bridge is a far thing from a full-on bridge. Building it to last a few days or weeks is much easier than building one to last years.

Second, having been a military combat engineer, we used to put up Bailey bridges or pontoon bridges in a matter of hours. And that’s with a handful of people. While those used pre-formed modern materials, the same concepts could be adapted to older materials and methods. The Bailey bridge is basically build on land then pushed out over rollers to extend over the water. A pontoon bridge needs only a few boats and some planks.

I’d want more details, but the time frame seems feasible. Especially with the manpower he had available.


Sent from my volcanic island lair using carrier pigeon.

 

[Jack by the hedge]

The single source appears to be Julius Caesar's own commentary on the Gallic Wars (written in the third person). Project Gutenberg provides a translation, from which this paragraph seems to be the entire description of the first bridge being built:

XVII.—Caesar, for those reasons which I have mentioned, had resolved to cross the Rhine; but to cross by ships he neither deemed to be sufficiently safe, nor considered consistent with his own dignity or that of the Roman people. Therefore, although the greatest difficulty in forming a bridge was presented to him, on account of the breadth, rapidity, and depth of the river, he nevertheless considered that it ought to be attempted by him, or that his army ought not otherwise to be led over. He devised this plan of a bridge. He joined together at the distance of two feet, two piles, each a foot and a half thick, sharpened a little at the lower end, and proportioned in length to the depth of the river. After he had, by means of engines, sunk these into the river, and fixed them at the bottom, and then driven them in with rammers, not quite perpendicularly, like a stake, but bending forward and sloping, so as to incline in the direction of the current of the river; he also placed two [other piles] opposite to these, at the distance of forty feet lower down, fastened together in the same manner, but directed against the force and current of the river. Both these, moreover, were kept firmly apart by beams two feet thick (the space which the binding of the piles occupied), laid in at their extremities between two braces on each side; and in consequence of these being in different directions and fastened on sides the one opposite to the other, so great was the strength of the work, and such the arrangement of the materials, that in proportion as the greater body of water dashed against the bridge, so much the closer were its parts held fastened together. These beams were bound together by timber laid over them in the direction of the length of the bridge, and were [then] covered over with laths and hurdles; and in addition to this, piles were driven into the water obliquely, at the lower side of the bridge, and these serving as buttresses, and being connected with every portion of the work, sustained the force of the stream: and there were others also above the bridge, at a moderate distance; that if trunks of trees or vessels were floated down the river by the barbarians for the purpose of destroying the work, the violence of such things might be diminished by these defences, and might not injure the bridge.

And Caesar's claim of 10 days flat, using local materials is the very next sentence:

XVIII.—Within ten days after the timber began to be collected, the whole work was completed, and the whole army led over.

 

[Andy_Ross]

They would have cut the timber as they needed it but think of it being built with logs in the round, not reduced to planks etc.

Roman legions were used for engineering when they weren't fighting. They were skilled at building earthworks, stone walling and timber construction. It was the legionaries that built Hadrian's Wall and all the forts along it.

8 Legions would have included hundreds of specialist engineers to do the 'technical' work with many tens of thousands of legionaries to do the physical stuff. Every legionary had a Dolabra axe as part of his kit. one side of the head was an entrenching tool, the other a sharp woodcutting axe, they would have made short work of timber for a bridge.

Iron spikes, brackets and miles of rope were part of a legions baggage train, ready for building fortifications and bridges where they were needed. There was also a lot of preformed timbers in the baggage ready to use in any construction.
There are the remains of several roman bridges near where I live, including a wooden and later stone Roman bridges across the Tees at Piercebridge. Some of the timbers that formed the piles of one of the wooden bridge can still be seen in the river bed.

 

[The Great Zaganza]

There are bridges and there are bridges.

Roman armies would build and use pontons to move across rivers when on campaign.
That way, a Legion could cross a large river in only 10 days.

Once they had pacified the place, they would build solid bridges for travel.

i think this is where the confusion comes from.

 

[smartcooky]

The single source appears to be Julius Caesar's own commentary on the Gallic Wars (written in the third person). Project Gutenberg provides a translation, from which this paragraph seems to be the entire description of the first bridge being built:

Quote:
XVII.—Caesar, for those reasons which I have mentioned, had resolved to cross the Rhine; but to cross by ships he neither deemed to be sufficiently safe, nor considered consistent with his own dignity or that of the Roman people. Therefore, although the greatest difficulty in forming a bridge was presented to him, on account of the breadth, rapidity, and depth of the river, he nevertheless considered that it ought to be attempted by him, or that his army ought not otherwise to be led over. He devised this plan of a bridge. He joined together at the distance of two feet, two piles, each a foot and a half thick, sharpened a little at the lower end, and proportioned in length to the depth of the river. After he had, by means of engines, sunk these into the river, and fixed them at the bottom, and then driven them in with rammers, not quite perpendicularly, like a stake, but bending forward and sloping, so as to incline in the direction of the current of the river; he also placed two [other piles] opposite to these, at the distance of forty feet lower down, fastened together in the same manner, but directed against the force and current of the river. Both these, moreover, were kept firmly apart by beams two feet thick (the space which the binding of the piles occupied), laid in at their extremities between two braces on each side; and in consequence of these being in different directions and fastened on sides the one opposite to the other, so great was the strength of the work, and such the arrangement of the materials, that in proportion as the greater body of water dashed against the bridge, so much the closer were its parts held fastened together. These beams were bound together by timber laid over them in the direction of the length of the bridge, and were [then] covered over with laths and hurdles; and in addition to this, piles were driven into the water obliquely, at the lower side of the bridge, and these serving as buttresses, and being connected with every portion of the work, sustained the force of the stream: and there were others also above the bridge, at a moderate distance; that if trunks of trees or vessels were floated down the river by the barbarians for the purpose of destroying the work, the violence of such things might be diminished by these defences, and might not injure the bridge.

A couple of things.

1. The "engines" he speaks of were piledrivers like these, which drive the piles at an angle as described

2. Caesar had 40,000 troops to call on. I have little doubt that a well-organised well-led group of 40,000 men could plausibly have built a bridge in 10 days.
.
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[smartcooky]

There are bridges and there are bridges.

Roman armies would build and use pontons to move across rivers when on campaign.
That way, a Legion could cross a large river in only 10 days.

Once they had pacified the place, they would build solid bridges for travel.

i think this is where the confusion comes from.

Firstly, I doubt a wooden pontoon bridge, made with essentially just logs, would be feasible on the Rhine. Its a wide, fast moving river, particularly where they were reputed to have been built (near where the town of Urmitz stands today). They would need to be in the order of 200m long. Sure, the US Army built pontoon bridges to cross the Rhine...

... but they were not made of unmilled logs. They used prefabricated steel pontoon boats similar to this....

Secondly, a pontoon bridge does not match the method of construction posted by Jack by the hedge

 

[Cosmic Yak]

More plausible would be that he did nothing. His visits across the Rhine were brief, and had no significant result.

The result was that the Germanic tribes did not venture across the Rhine to attack Rome for centuries afterwards.
It also gave Caesar added glory, so there was a benefit for him too.

He may have also used boats, which apparently were available.

The point was to demonstrate Roman power and technological prowess. He was making a statement.
As a general point, Caesar's chronicles, whilst obviously self-aggrandising, do seem to be reasonably historically accurate. I see no reason to dispute them on this matter. Happy to be corrected on this, as ever.

 

[Andy_Ross]

Firstly, I doubt a wooden pontoon bridge, made with essentially just logs, would be feasible on the Rhine. Its a wide, fast moving river, particularly where they were reputed to have been built (near where the town of Urmitz stands today). They would need to be in the order of 200m long. Sure, the US Army built pontoon bridges to cross the Rhine...

[qimg]https://www.dropbox.com/s/x02xcgnn6x6q5db/ww2pontoonbridge.png?raw=1[/qimg]

... but they were not made of unmilled logs. They used prefabricated steel pontoon boats similar to this....

[qimg]https://www.dropbox.com/s/bw757q1dbkvk8ls/ww2pontoonboat.jpg?raw=1[/qimg]

Secondly, a pontoon bridge does not match the method of construction posted by Jack by the hedge

But the Romans were not crossing with tanks, they were men on foot and only needed it to stand for one season.

Rome built wooden bridges in other locations at similar river crossings.
As a temporary structure it would be fine.

At Piercebridge on the Tees there are the remains of two Roman bridges, one stone based with wooden decking and an earlier all wooden bridge. Bases of wooden piles can still be seen on the river bed from the earlier bridge. It was washed away regularly by winter floods and boulders being washing down against it.
Time Team did a dig there in one of their episodes. They also did one on the first bridge across the Thames at London, that was wooden too.

Point is the Romans had a large workforce to build wooden bridges quickly.

 

[smartcooky]

But the Romans were not crossing with tanks, they were men on foot and only needed it to stand for one season.

Rome built wooden bridges in other locations at similar river crossings.
As a temporary structure it would be fine.

At Piercebridge on the Tees there are the remains of two Roman bridges, one stone based with wooden decking and an earlier all wooden bridge. Bases of wooden piles can still be seen on the river bed from the earlier bridge. It was washed away regularly by winter floods and boulders being washing down against it.
Time Team did a dig there in one of their episodes. They also did one on the first bridge across the Thames at London, that was wooden too.

Firstly, the point I was making is that a pontoon bridge across the Rhine would be unlikely (and as I said earlier, it does not match the construction description given by Jack by the Hedge). That is not to say the Romans didn't build and use pontoon bridges - they did as shown in this woodcut of Roman Legionnaires crossing the River Ister (Danube) during one of the campaigns of Marcus Aurelius in the Marcomannic Wars from about 162 to 180AD.

The problem is that the Rhine is quite a fast flowing river, and in Caesar's time, it was wide where he wanted to cross it; over 400m. Building a pontoon bridge on a wide fast flowing river is a considerable engineering challenge.

Secondly, it wasn't just footsoldiers that the Romans would have to take across the bridges. They were in Germania for 18 days, so they would have needed a supply line. There were pack animals such as mules and asses, and they also drove cattle on the hoof for slaughter to feed the soldiers. Then there are the supply wagons for materiel - the plaustrum, a two-wheeled wagon drawn by oxen, the carpentum, a two-wheeler drawn by mules and the carrus, a four-wheeler either drawn by mules or draught horses in teams of two or four depending on the weight being drawn.

Point is the Romans had a large workforce to build wooden bridges quickly.

Yes, I think I said 40,000 troops in the case in question.

 

[qarnos]

Building a pontoon bridge on a wide fast flowing river is a considerable engineering challenge.

It's not if your bridge doesn't need to really exist and you just want to convince people it did

 

[TurkeysGhost]

I was under the impression that Roman legions were famous for their skill in rapidly building things in the field.

 

[qarnos]

I was under the impression that Roman legions were famous for their skill in rapidly building things in the field.

Building a Castra, which you came prepared to do to a standardised plan, is a completely different thing to building a makeshift bridge over a span of river you have never encountered and had not planned for.

Why is everyone being so defensive? It's not like I insulted yo mama! It's a very interesting question to ponder over, especially since this is supposedly a skeptics forum. There is literally no evidence for this apart from Caesar's own word! JFC.

 

[TurkeysGhost]

Building a Castra, which you came prepared to do to a standardised plan, is a completely different thing to building a makeshift bridge over a span of river you have never encountered and had not planned for.

Why is everyone being so defensive? It's not like I insulted yo mama! It's a very interesting question to ponder over, especially since this is supposedly a skeptics forum. There is literally no evidence for this apart from Caesar's own word! JFC.

I don't mean to come across as defensive. It's an interesting question, and the point that Caesar is the source for these self-serving tales of adventuring abroad in bandit country is well taken.

I would just point out that legions who are famous for quickly slapping up fortifications probably are very good builders. Even using a standardized plan requires general building/carpentry skills. These are soldiers who have had building efficiently drilled into them as a matter of military training. It doesn't strike me as totally implausible that they could put together a temporary bridge so quickly.

 

[Andy_Ross]

Firstly, the point I was making is that a pontoon bridge across the Rhine would be unlikely (and as I said earlier, it does not match the construction description given by Jack by the Hedge). That is not to say the Romans didn't build and use pontoon bridges - they did as shown in this woodcut of Roman Legionnaires crossing the River Ister (Danube) during one of the campaigns of Marcus Aurelius in the Marcomannic Wars from about 162 to 180AD.

[qimg]https://www.dropbox.com/s/uvcicvnqfz8bcrh/pontoonwoodcut.jpg?raw=1[/qimg]

The problem is that the Rhine is quite a fast flowing river, and in Caesar's time, it was wide where he wanted to cross it; over 400m. Building a pontoon bridge on a wide fast flowing river is a considerable engineering challenge.

Secondly, it wasn't just footsoldiers that the Romans would have to take across the bridges. They were in Germania for 18 days, so they would have needed a supply line. There were pack animals such as mules and asses, and they also drove cattle on the hoof for slaughter to feed the soldiers. Then there are the supply wagons for materiel - the plaustrum, a two-wheeled wagon drawn by oxen, the carpentum, a two-wheeler drawn by mules and the carrus, a four-wheeler either drawn by mules or draught horses in teams of two or four depending on the weight being drawn.



Yes, I think I said 40,000 troops in the case in question.

Rhine wasn't as fast flowing 'back then' though, as you say it was wider, the land around was not 'improved' or drained like it is today and forced in to a narrower channel.
It was the same with the Thames, when the first wooden bridge was put across at London the river was wider but slower. Marshy ground either side was crossed by a causeway.
Time Team did a dig on the Thames foreshore at the site of the original bridge.