In the first century BCE, present-day Martigny was an oppidum or vicus of a Celtic tribe, the Veragri. It was then called Octodurus or Octodurum. When Julius Caesar was in Gaul (57-56 BCE), he sent Servius Galba with the twelfth legion and some cavalry into the country of the Nantuates, Veragri, and Seduni. His purpose in sending this force was to open the pass over the Alps, the pass of the Great St. Bernard, by which road the "mercatores" had been used to travel at great risk, and with the payment of great tolls. ("B. G." iii. 1.) The people of the Alps allowed the Italian merchants to pass, because if they plundered them the merchants would not come; but they got as much out of them as they could. Galba, after taking many strong places, and receiving the submission of the people, sent off two cohorts into the country of the Nantuates, and with the remaining cohorts determined to winter in Octodurus, which was in a valley with no great extent of level ground near it, confined on all sides by very lofty mountains. There is some level ground at Martigny, and the valley of the Rhone at this part is not very narrow. Caesar says that the town of Octodurus was divided into parts by a river, but he does not mention the river's name. It is the Dranse. Galba gave one part of the town to the Galli to winter in, and assigned the other to his troops. He fortified himself with a ditch and rampart, and thought he was safe. He was, however, suddenly attacked by the Galli before his defences were complete or all his supplies were brought into the camp. Thus began the Battle of Octodurus. The Romans obstinately defended themselves in a six hours' fight; when, seeing that they could no longer keep the enemy out, they made a sortie, which was successful. The Romans estimated the Galli at more than 30,000, and Caesar says that more than a third part were destroyed. The slaughter of the enemy was prodigious, which has been made an objection to Caesar's veracity, or to Galba's, who made his report to the commander. It has also been objected that the valley is not wide enough at Martigny to hold the 30,000 men. There may be error in the number that attacked, and also in the number who died. After this escape Galba prudently withdrew his troops, and marching through the country of the Nantuates reached the land of the Allobroges, where he wintered.