In the spring, when the grass had grown enough to provide food for their horses and oxen, the barbarians put themselves in motion. Marius left the Cimbri to take their agreed-upon route to the north-east, and waited for the Teutons and Ambrons. He allowed them to cross the Rhône, and they drew up before his fortified camp at St. Gabriel on the westernmost spur of the Alpilles, and shouted defiance and insult to his troops. But he restrained the Romans from attacking them. Their ambition, he told them, should not now be for triumphs and trophies but to dispel the dreadful storm that hung over them and to save Italy itself from destruction.

The barbarians made a half-hearted attack upon the Roman camp, which was easily repulsed, and then moved on. It was said that though they moved forward without pause it took them six days to pass the camp, so vast were their numbers. They were indeed nations and not only armies on the march. The cumbrous house-wagons with which they moved were their homes, for their wives and families were with them, and none had been left behind.

The hot-blooded Romans were by now inured to their insults, one of which was to shout the question whether they had any commands for their wives in Italy, for they would shortly be with them. One can picture them sulkily watching from the high ground, where they were encamped, the interminable rabble moving on day after day, and wondering whether they would ever end. But directly the barbarians had passed Marius struck camp and followed them, not by the straight Roman road which they had taken along the valley, but by the heights to the south, and observed all their movements, himself out of sight.

At Aix the Ambrons detached themselves from their allies to make a descent upon Marseilles. Marius had fixed upon a hill for his camp at Les Milles, four miles to the south of Aix. It was unexceptionable in point of strength, but afforded little water. By this circumstance, says Plutarch, they tell us he wanted to excite his soldiers to action, and when many of them complained of thirst he pointed to the river Arc, which ran close by the enemy's camp, and told them that thence they must buy water with their blood.

It was this lack of water that precipitated the contest. The soldiers obeyed the order first of all to fortify their camp, but the servants of the army could not be restrained from going down to the river for water. Some of the enemy were bathing in the hot springs that well up in this place, others were eating. These were cut off by the camp-followers, others came to their assistance, and the Roman soldiers rushed down from the hill to rescue their servants. The engagement became general, and the Ambrons were beaten with great loss, the river being choked with their dead.

This was a good beginning, but the Romans spent the night in fear of attack, for their camp was not yet fortified. "There remained yet many myriads of the barbarians unconquered; and such of the Ambrons as escaped mixing with them, a cry was heard all night not like the sighs and groans of men, but like the howling and bellowing of wild beasts. As this came from such an innumerable host the neighbouring mountains and the hollow banks of the river returned the sound, and the horrid din filled all the plains. The Romans felt a sense of terror, and Marius himself was filled with apprehension at the idea of a tumultuous night engagement."

Fortunately, however, the barbarians did not attack, but after a day and a night moved on and joined the Teutons, who were passing along the road to the north of the river Arc. At this point Plutarch's narrative becomes confused, for he does not effectually distinguish the fields of the two battles, which were fought two days apart. It is here that Mr. Baring-Gould's careful investigations are valuable in elucidating the narrative.

The barbarians halted at the Roman station Tegulata, now the hamlet of La Petite Pugère, a day's march from Aix. Marius crossed the river and kept to the south of it till he reached Trets. At his rear he had a fortified camp on Mount Olympus, to the north of the barbarians was another fortified Roman camp, Panis Annonæ, still called Pain de Munition. To this he had sent the day before an officer with three thousand men, who had made their way to it protected by the range of Mont Victoire. His plan must have been made long before, from a careful consideration of the route the enemy was likely to take, and the commanding positions fortified and provisioned. The barbarians were in a trap, but did not yet know it.

In the morning the enemy awoke to see the bulk of the Roman army drawn up on the slope of a hill to the south of their camp. They could not contain their impatience until the army advanced into the plain, and received their first setback by rushing up to attack it. Marius sent his officers among the troops with orders to stand still and await the onslaught. When the enemy was within reach they were to throw their javelins, and then, sword in hand, press them down with their shields. He knew that the slope was so slippery that the blows of the enemy would be delivered with no great force and that they could not keep any close order.

When this attack had been repulsed the Romans crossed the river and fell upon the main body of the enemy, who was beginning to form again. But at the same time the ambushed troops descended from Panis Annonæ in the rear, and panic seized the barbarians. The slaughter was terrific. Plutarch gives the number of killed as a hundred thousand of the enemy alone. Some accounts double the number, and give that of the prisoners as another eighty thousand. It is said also that three hundred thousand of the camp-followers and women were either killed or sold into slavery. It was the extermination not of an army but of a nation.