Gaius Julius Caesar (13 July 100 - 15 March 44 BCE), Roman statesman, general, author, famous for the conquest of Gaul (modern France and Belgium) and his subsequent coup d'état. He changed the Roman republic into a monarchy and laid the foundations of a truly Mediterranean empire.
In the spring of 55 BCE, Julius Caesar's soldiers attacked a large group of Germanic refugees during an armistice. Many people, belonging to the tribes of the Usipetes and Tencteri, were massacred (text). The Roman Senate discussed this shameful behavior, and Caesar dediced to divert the Senate's attention. During the early summer, he crossed the Rhine and invaded Germania; later, he even invaded Britain. These operations had little military purpose, but the Senate was impressed and that was what mattered.
The translation of Caesar's War in Gaul 4.16-19 was made by Anne and Peter Wiseman.
[4.16.1] With the German war concluded,note[Caesar had repelled an invasion of the Germanic Usipetes and Tencteri.] I decided that I must cross the Rhine. Several reasons prompted me. The strongest was that I could see the Germans were all too ready to cross into Gaul, and I wanted them to have reasons of their own for anxiety when they realized that an army of the Roman people could and would cross the Rhine.
[4.16.2] There was also the fact that the section of cavalry of the Usipetes and the Tencteri, which, as I have already mentioned, had crossed the Meuse in search of plunder and grain and so had not taken part in the battle, had crossed the Rhine after the rout of their countrymen, entered the territory of the Sugambri and joined forces with them.note[In other words, Caesar wanted to prevent a second invasion by the Usipetes and Tencteri.]
[4.16.3] When I sent messengers to the Sugambri to demand the surrender of those who had made war on me and on Gaul, they replied that the Rhine was the limit of Roman power:
[4.16.4] if I thought the Germans had no right to cross into Gaul against my will, why should I claim any power or authority on the German side of the Rhine?
[4.16.5] Then too there was the fact that the Ubians - the only tribe across the Rhine who had sent envoys to me, established ties of friendship, and given hostages - were urgently begging me to go to their help because they were being severely harassed by the Suebians.note[The half-Celtic Ubians were Roman allies, now threatened by the Suebians, a "real" Germanic tribe.]
[4.16.6] If it was impossible for me to do that because of political preoccuparations, they asked me merely to take my army across the Rhine; that would be enough to give them help and provide them with confidence for the future. [...]
[4.16.8] They promised to provide a large number of boats to get the army across the river.
[4.17.1] These were the reasons that had made me decide to cross the Rhine.note[Caesar ignores his real motive: that he had attacked the Usipetes and Tencteri during peace time. The Roman Senate felt it had to do something against this criminal behavior. Caesar was aware of this, and wanted to impress the Senate by an invasion of Germania. Later, he even crossed to Britain.] However, I thought that to cross in boats would be too risky, and would not be fitting for my own prestige and that of Rome.
[4.17.2] And so, even though building a bridge involved enormous difficulties, because of the breadth and depth of the river and its strong current, that is what I thought I must attempt, or else give up any thoughts of taking the army across.
[4.17.3] This is the method I used in building the bridge. Two piles a foot and a half thick, slightly pointed at their lower ends and of lengths dictated by the varying depth of the river, were fastened together two feet apart.
[4.17.4] We used tackle to lower these into the river, where they were fixed in the bed and driven home with piledrivers, not vertically, as piles usually are, but obliquely, leaning in the direction of the current.
[4.17.5] Opposite these, 40 feet lower down the river, two more piles were fixed, joined together in the same way, though this time against the force of the current.
[4.17.6] These two pairs were then joined by a beam two feet wide, whose ends fitted exactly into the spaces between the two piles of each pair. The pairs were kept apart from each other by means of braces that secured each pile to the end of the beam.
[4.17.7] So the piles were kept apart, and held fast in the opposite direction, the structure being so strong and the laws of physics such that the greater the force of the current, the more tightly were the timbers held in place.
[4.17.8] A series of these piles and beams was put in position and connected by lengths of timber set across them, with poles and bundles of sticks laid on top.
[4.17.9] The structure was strong, but additional piles were driven in obliquely on the downstream side of the bridge; these were joined with the main structure and acted as buttresses to take the force of the current.
[4.17.10] Other piles too were fixed a little way upstream from the bridge so that if the natives sent down tree trunks or boats to demolish it, these barriers would lessen their impact and prevent the bridge being damaged.
[4.18.1] Ten days after the collection of the timber was begun, the work was completed and the army led across.
[4.18.2] I left a strong guard at each end of the bridge and then marched into the territory of the Sugambri.
[4.18.3] Meanwhile deputations came to me from several tribes asking for peace and friendship. I replied courteously and told them to have hostages brought to me.
[4.18.4] From the moment we had started building the bridge, the Sugambri had been preparing for flight. They were urged to do so by those of the Tencteri and the Usipetes who were with them, and so they left their own country and disappeared into uninhabited forests, taking all their belongings with them.
[4.19.1] I stayed a few days in their territory, burning all their villages and buildings and cutting down their crops. Then I returned to the country of the Ubians. I promised this people help if they were harassed by the Suebians, and they gave me the following information. When the Suebians had learned from their scouts that a bridge was being built, they followed their usual custom and called a council. They sent messengers to every part of their country telling their people to leave their oppida:note[Usually, thus word means hill-forts, but here, it probable means fortified villages.]
[4.19.2] they were to take their women, their children, and all their property into the forests and then all men capable of fighting were to assemble in one place, that chosen being about the middle of their territory. There, the Ubians informed me, the Suebians were waiting for us to arrive and that was the place where they had decided to fight it out.
[4.19.3] On receiving this information, I crossed back into Gaul,note[A euphemism. Caesar leaves Germania when his enemies start to mobilize.] breaking the bridge behind me.
[4.19.4] I had accomplished all the objectives that had made me decide to take my army across the Rhine - to intimidate the Germans, to punish the Sugambri, to relieve the Ubians from Suebic harassment. We had spent eighteen days in all across the Rhine and I considered I had done all that honor or interest required.