Under the command of the Proconsul Julius Caesar, the Roman army marched at speed through the French countryside in the early spring of 58 BC. Its objective was to halt the advance of the Helvetii, a Swiss tribe that had been pouring into Roman territory in southern France. Caesar's men were fully armed and ready to respond to a surprise attack.
At the head of the army column were lightly armed auxiliaries, recruited from the Italian provinces, who acted as scouts - with particular orders to watch out for the threat of ambushes. The vanguard, made up of detachments of cavalry and heavy infantry, followed. Next came the soldiers detailed to lay out the camp that would be built when the army halted for the night. "Pioneers", whose responsibility was to find the best way over or around natural obstacles on the route, were the next group.
After the commanders, the camp followers
The creak of carts heralded the approach of the proconsul's baggage train. A clatter of hooves, and Julies Caesar himself, his commanders and key staff officers rode by, resplendent in red cloaks, with their cavalry escort. Next were the legions, the main body of the army. At the head of each rode its commander, followed by the legion's standards and trumpeters, with the legionaries themselves marching in six-man ranks. Further cohorts of auxiliaries preceded the rearguard, which was made up of cavalry. A ragtag of camp followers, including food and bread sellers, prostitutes and even slave dealers ready to snap up prisoners of war, trailed after the army.
Julius Caesar – the military governor of Cisalpine Gaul (Northern Italy) and Transalpine Gaul (central and northern France, Belgium and much of Switzerland) - had made careful preparations before launching the campaign. His first task had been to draw together his scattered forces.
The Roman usually went into camps during the winter months, and in Gaul the troops were widely dispersed to ensure that people did not break the peace. Caesar also enlisted the help of local tribes who were enemies of the Helvetii, and with their aid was able to put a force of around 35,000 in the field.
His next job was to build up his supplies in readiness for the campaign ahead. Food was the most important. The Roman soldier on campaign lived on a diet of whole meal biscuits, bacon and cheese - all of which could be salted or otherwise preserved - washed down with sour wine. The army did occasionally forage for food while on the march, but this was not encouraged since it led troops to spread out, making them vulnerable. The army also needed to cut large amounts of timber, because it planned to build fortifications in the path of the Helvetii, especially to stop the tribe crossing the River Rhône.
Caesar had a lean, well-organized military machine at his disposal. He had three legions in Gaul, each with a strength of around 5,000-6,000 men, divided into ten cohorts. Each cohort consisted of six centuries of 80-100 men, divided into sections of eight to ten. The legion also had a force of 120 cavalrymen, often largely made up of non-Roman citizens, particularly the Numidians (from modern Algeria in north Africa) and Germans. They were used as scouts and dispatch riders. The legion was commanded by a "legate", assisted by six tribunes, but the backbone of the legion's officer corps were the centurions, battle-hardened army veterans each of whom commanded a century.
At the end of each day's march, the army set up camp for the night, using guy ropes and pegs to erect a square city of leather tents. The legionaries slept eight to a tent. The camp was protected on all four sides by a ditch and an earth rampart topped with a palisade made of sharp wooden stakes, and had four large gates to allow the soldiers to sally forth quickly.
Reveille - then quick march
These fortified barracks were always constructed to an identical plan, and the familiar layout had significant advantages. Because each soldier knew beforehand exactly what to do, a camp could be thrown up very quickly. Faced with a surprise attack - even in darkness - the legionaries and auxiliaries knew exactly where they were. The camp was guarded by sentries through the night. In the morning, a bugle blared the signal for the soldiers to take their tents down; a second call gave the order to load the baggage animals and prepare to march.
These tried and tested methods worked well for Julius Caesar. In July, his experienced soldiers decisively defeated the Helvetii in central France, and forced them to return to their homes in Switzerland.