The flame of war now blazed up far and wide. The Lusitanians on the left bank of the Tagus, led by Caucaenus, threw themselves on the Celtici subject to the Romans (in Alentejo), and took away their town Conistorgis. The Lusitanians sent the standards taken from Mummius to the Celtiberians at once as an announcement of victory and as a warning; and among these, too, there was no want of ferment. Two small Celtiberian tribes in the neighbourhood of the powerful Arevacae (about the sources of the Douro and Tagus), the Belli and the Titthi, had resolved to settle together in Segeda, one of their towns. While they were occupied in building the walls, the Romans ordered them to desist, because the Sempronian regulations prohibited the subject communities from founding towns at their own discretion; and they at the same time required the contribution of money and men which was due by treaty but for a considerable period had not been demanded. The Spaniards refused to obey either command, alleging that they were engaged merely in enlarging, not in founding, a city, and that the contribution had not been merely suspended, but remitted by the Romans. Thereupon Nobilior appeared in Hither Spain with an army of nearly 30,000 men, including some Numidian horsemen and ten elephants. The walls of the new town of Segeda still stood unfinished: most of the inhabitants submitted. But the most resolute men fled with their wives and children to the powerful Arevacae, and summoned these to make common cause with them against the Romans. The Arevacae, emboldened by the victory of the Lusitanians over Mummius, consented, and chose Carus, one of the Segedan refugees, as their general. On the third day after his election the valiant leader had fallen, but the Roman army was defeated and nearly 6000 Roman burgesses were slain; the 23rd day of August, the festival of the Volcanalia, was thenceforth held in sad remembrance by the Romans. The fall of their general, however, induced the Arevacae to retreat into their strongest town Numantia (Guarray, a Spanish league to the north of Soria on the Douro), whither Nobilior followed them. Under the walls of the town a second engagement took place, in which the Romans at first by means of their elephants drove the Spaniards back into the town; but while doing so they were thrown into confusion in consequence of one of the animals being wounded, and sustained a second defeat at the hands of the enemy again issuing from the walls. This and other misfortunes-- such as the destruction of a corps of Roman cavalry despatched to call forth the contingents--imparted to the affairs of the Romans in the Hither province so unfavourable an aspect that the fortress of Ocilis, where the Romans had their chest and their stores, passed over to the enemy, and the Arevacae were in a position to think, although without success, of dictating peace to the Romans. These disadvantages, however, were in some measure counterbalanced by the successes which Mummius achieved in the southern province. Weakened though his army was by the disaster which it had suffered, he yet succeeded with it in defeating the Lusitanians who had imprudently dispersed themselves on the right bank of the Tagus; and passing over to the left bank, where the Lusitanians had overrun the whole Roman territory, and had even made a foray into Africa, he cleared the southern province of the enemy.
To the northern province in the following year (602) the senate sent considerable reinforcements and a new commander-in-chief in the place of the incapable Nobilior, the consul Marcus Claudius Marcellus, who had already, when praetor in 586, distinguished himself in Spain, and had since that time given proof of his talents as a general in two consulships. His skilful leadership, and still more his clemency, speedily changed the position of affairs: Ocilis at once surrendered to him; and even the Arevacae, confirmed by Marcellus in the hope that peace would be granted to them on payment of a moderate fine, concluded an armistice and sent envoys to Rome. Marcellus could thus proceed to the southern province, where the Vettones and Lusitanians had professed submission to the praetor Marcus Atilius so long as he remained within their bounds, but after his departure had immediately revolted afresh and chastised the allies of Rome. The arrival of the consul restored tranquillity, and, while he spent the winter in Corduba, hostilities were suspended throughout the peninsula. Meanwhile the question of peace with the Arevacae was discussed at Rome. It is a significant indication of the relations subsisting among the Spaniards themselves, that the emissaries of the Roman party subsisting among the Arevacae were the chief occasion of the rejection of the proposals of peace at Rome, by representing that, if the Romans were not willing to sacrifice the Spaniards friendly to their interests, they had no alternative save either to send a consul with a corresponding army every year to the peninsula or to make an emphatic example now. In consequence of this, the ambassadors of the Arevacae were dismissed without a decisive answer, and it was resolved that the war should be prosecuted with vigour. Marcellus accordingly found himself compelled in the following spring (603) to resume the war against the Arevacae. But--either, as was asserted, from his unwillingness to leave to his successor, who was to be expected soon, the glory of terminating the war, or, as is perhaps more probable, from his believing like Gracchus that a humane treatment of the Spaniards was the first thing requisite for a lasting peace--the Roman general after holding a secret conference with the most influential men of the Arevacae concluded a treaty under the walls of Numantia, by which the Arevacae surrendered to the Romans at discretion, but were reinstated in their former rights according to treaty on their undertaking to pay money and furnish hostages.
When the new commander-in-chief, the consul Lucius Lucullus, arrived at head-quarters, he found the war which he had come to conduct already terminated by a formally concluded peace, and his hopes of bringing home honour and more especially money from Spain were apparently frustrated.