Gladly would Mithradates have avoided undertaking so arduous a work singlehanded. His nearest and natural ally was the great-king Tigranes; but that shortsighted man declined the proposal of his father-in-law. So there remained only the insurgents and the pirates.
Mithradates was careful to place himself in communication with both, by despatching strong squadrons to Spain and to Crete. A formal treaty was concluded with Sertorius[11], by which Rome ceded to the king Bithynia, Paphlagonia, Galatia, and Cappadocia - all of them, it is true, acquisitions which needed to be ratified on the field of battle. More important was the support which the Spanish general gave to the king, by sending Roman officers to lead his armies and fleets. The most active of the emigrants inthe east, Lucius Magius and Lucius Fannius, were appointed by Sertorius as his representatives at the court of Sinope. From the pirates also came help; they flocked largely to the kingdom of Pontus, and by their means especially the king seems to have succeeded in forming a naval force imposing by the number as well as by the quality of the ships. His main support still lay in his own forces, with which the king hoped, before the Romans should arrive in Asia, to make himself master of their possessions there; especially as the financial distress produced in the province of Asia by the Sullan war-tribute, the aversion of Bithynia towards the new Roman government, and the elements of combustion left behind by the desolating war recently brought to a close in Cilicia and Pamphylia, opened up favourable prospects to a Pontic invasion.
There was no lack of stores; 2,000,000 medimni of grain lay in the royal granaries. The fleet and the men were numerous and well exercised, particularly the Bastarnian mercenaries, a select corps which was a match even for Italian legionaries. On this occasion also it was the king who took the offensive. A corps under Diophantus advanced into Cappadocia, to occupy the fortresses there and to close the way to the kingdom of Pontus against the Romans; the leader sent by Sertorius, the propraetor Marcus Marius, went in company with the Pontic officer Eumachus to Phrygia, with a view to rouse the Roman province and the Taurus mountains to revolt; the main army, above 100,000 men with 16,000 cavalry and 100 scythe-chariots, led by Taxiles and Hermocrates under the personal superintendence of the king, and the war-fleet of 400 sail commanded by Aristonicus, moved along the north coast of Asia Minor to occupy Paphlagonia and Bithynia.
On the Roman side there was selected for the conduct of the war in the first rank the consul of 680, Lucius Lucullus, who as governor of Asia and Cilicia was placed at the head of the four legions stationed in Asia Minor and of a fifth brought by him from Italy, and was directed to penetrate with this army, amounting to 30,000 infantry and 1600 cavalry, through Phrygia into the kingdom of Pontus. His colleague Marcus Cotta proceeded with the fleet and another Roman corps to the Propontis, to cover Asia and Bithynia. Lastly, a general arming of the coasts and particularly of the Thracian coast more immediately threatened by the Pontic fleet, was enjoined; and the task of clearing all the seas and coasts from the pirates and their Pontic allies was, by extraordinary decree, entrusted to a single magistrate, the choice falling on the praetor Marcus Antonius, the son of the man who thirty years before had first chastised the Cilician corsairs[12]. Moreover, the senate placed at the disposal of Lucullus a sum of 72,000,000 sesterces (700,000 pounds), in order to build a fleet; which, however, Lucullus declined. From all this we see that the Roman government recognized the root of the evil in the neglect of their marine, and showed earnestness in the matter at least so far as their decrees reached.
Thus the war began in 680 at all points. It was a misfortune for Mithradates, that at the very moment of his declaring war the Sertorian struggle reached its crisis, by which one of his principal hopes was from the outset destroyed, and the Roman government was enabled to apply its whole power to the maritime and Asiatic contest. In Asia Minor on the other hand Mithradates reaped the advantages of the offensive, and of the great distance of the Romans from the immediate seat of war. A considerable number of cities in Asia Minor opened their gates to the Sertorian propraetor who was placed at the head of the Roman province, and they massacred, as in 666, the Roman families settled among them: the Pisidians, Isaurians, and Cilicians took up arms against Rome. The Romans for the moment had no troops at the points threatened. Individual energetic men attempted no doubt at their own hand to check this mutiny of the provincials; thus on receiving accounts of these events the young Gaius Caesar left Rhodes where he was staying on account of his studies, and with a hastily-collected band opposed himself to the insurgents; but not much could be effected by such volunteer corps. Had not Deiotarus, the brave tetrarch of the Tolistobogii - a Celtic tribe settled around Pessinus - embraced the side of the Romans and fought with success against the Pontic generals, Lucullus would have had to begin with recapturing the interior of the Roman province from the enemy. But even as it was, he lost in pacifying the province and driving back the enemy precious time, for which the slight successes achieved by his cavalry were far from affording compensation. Still more unfavourable than in Phrygia was the aspect of things for the Romans on the north coast of Asia Minor. Here the great Pontic army and the fleet had completely mastered Bithynia, and compelled the Roman consul Cotta to take shelter with his far from numerous force and his ships within the walls and port of Chalcedon, where Mithradates kept them blockaded.
This blockade, however, was so far a favourable event for the Romans, as, if Cotta detained the Pontic army before Chalcedon and Lucullus proceeded also thither, the whole Roman forces might unite at Chalcedon and compel the decision of arms there rather than in the distant and impassable region of Pontus. Lucullus did take the route for Chalcedon; but Cotta, with the view of executing a great feat at his own hand before the arrival of his colleague, ordered his admiral Publius Rutilius Nudus to make a sally, which not only ended in a bloody defeat of the Romans, but also enabled the Pontic force to attack the harbour, to break the chain which closed it, and to burn all the Roman vessels of war which were there, nearly seventy in number. On the news of these misfortunes reaching Lucullus at the river Sangarius, he accelerated his march to the great discontent of his soldiers, in whose opinion Cotta was of no moment, and who would far rather have plundered an undefended country than have taught their comrades to conquer. His arrival made up in part for the misfortunes sustained: the king raised the siege of Chalcedon, but did not retreat to Pontus; he went southward into the old Roman province, where he spread his army along the Propontis and the Hellespont, occupied Lampsacus, and began to besiege the large and wealthy town of Cyzicus. He thus entangled himself more and more deeply in the blind alley which he had chosen to enter, instead of - which alone promised success for him - bringing the wide distances into play against the Romans.