Although only his books on the Roman Civil Wars survive in their entirety, large parts of other books have also come down to us. Fortunately, the Mithridatic wars belong to these better preserved parts. They are a very valuable source for the history of the Roman expansion in what is now called Turkey.
The translation was made by Horace White; notes by Jona Lendering.
 "The Bithyniansnote[Speech of Pelopidas in 88 BCE.] were not wrong in what they told you lately about the kings of Egypt and Syria. Not only are these likely to help us if war breaks out, but also your newly acquired province of Asia, and Greece, and Africa, and a considerable part of Italy itself, which even now wages implacable war against you because it cannot endure your greed.note[A reference to the Social War.]
Before you are able to compose this strife, you attack Mithridates and set Nicomedes and Ariobarzanes on him by turns, and you say, forsooth, that you are our friends and allies. You pretend to be so, and yet you act like enemies. Come now, if at last the consequences of your acts have put you in a better frame of mind, either restrain Nicomedes from injuring your friends and allies (in which case I promise that king Mithridates shall help you to put down the rebellion in Italy), or throw off the mask of friendship for us, or let us go to Rome and settle the dispute there."
So spoke Pelopidas. The Romans considered his speech insolent and ordered Mithridates to let Nicomedes and Cappadocia alone (for they had again restored Ariobarzanes to the latter). They also ordered Pelopidas to leave their camp immediately, and not to return unless the king obeyed their commands. Having given this answer they sent him away under guard lest he should inveigle some persons on the road.
First Mithridatic War
 After they had finished speaking they did not wait to hear what the Senate and people of Rome would think about such a great war, but began to collect forces from Bithynia, Cappadocia, Paphlagonia, and the Galatians of Asia. As soon as Lucius Cassius, the proconsul of Asia,note[The first name of the proconsul of Asia was not Lucius, but Gaius.] had his own army in readiness all the allied forces were assembled.
Then they were put in separate divisions and sent into camp, Cassius on the boundary of Bithynia and Galatia, Maniusnote[Manius Aquilius.] on Mithridates' line of march to Bithynia, and Oppius,note[Quintus Oppius was propraetor of Cilicia.] the third general, among the mountains of Cappadocia. Each of these had about 40,000 men, horse and foot together. They had also a fleet under command of Minucius Rufus and Gaius Popillius at Byzantium, guarding the mouth of the Euxine. Nicomedes was present with 50,000 foot and 6,000 horse under his command. Such was the total strength of the forces brought together.
Mithridates had in his own army 250,000 foot and 40,000 horse, 300 ships with decks, 100 with two banks of oars each, and other apparatus in proportion. He had for generals Neoptolemus and Archelaus, two brothers. The king took charge of the greater number in person. Of the allied forces Arcathias, the son of Mithridates, led 10,000 horse from Armenia Minor, and Doryalus commanded the phalanx. Craterus had charge of 130 war chariots. So great were the preparations on either side when the Romans and Mithridates first came in conflict with each other, about the 173d Olympiad.
 When Nicomedes and the generals of Mithridates came in sight of each other in a wide plain bordered by the river Amnias, they drew up their forces for battle. Nicomedes had his entire army in hand; Neoptolemus and Archelaus had only their light infantry and the cavalry of Arcathias and a few chariots; for the phalanx had not yet come up.
They sent forward a small force to seize a rocky hill in the plain lest they should be surrounded by the Bithynians, who were much more numerous. When Neoptolemus saw his men driven from the hill he was still more in fear of being surrounded. He advanced with haste to their assistance, at the same time calling on Arcathias for help.
When Nicomedes perceived the movement, he sought to meet it by a similar one. Thereupon a severe and bloody struggle ensued. Nicomedes prevailed and put the Mithridateans to flight until Archelaus, advancing from the right flank, fell upon the pursuers, who were compelled to turn their attention to him. He yielded little by little in order that the forces of Neoptolemus might have a chance to rally. When he judged that they had done so sufficiently, he advanced again. At the same time the scythe-bearing chariots made a charge on the Bithynians, cutting some of them in two, and tearing others to pieces.
The army of Nicomedes was terrified at seeing men cut in halves and still breathing, or mangled in fragments and their parts hanging on the scythes. Overcome rather by the hideousness of the spectacle than by loss of the fight, fear took possession of their ranks. While they were thus thrown into confusion, Archelaus attacked them in front, and Neoptolemus and Arcathias, who had turned about, assailed them in the rear.
They fought a long time facing both ways. After the greater part of his men had fallen, Nicomedes fled with the remainder into Paphlagonia, although the Mithridatean phalanx had not come into the engagement at all. His camp was captured, together with a large sum of money and many prisoners. All these Mithridates treated kindly and sent to their homes with supplies for the journey, thus gaining a reputation for clemency among his enemies.
 This first engagement of the Mithridatic war alarmed the Roman generals, because they had kindled so great a strife precipitately, without good judgment, and without any public decree. A small number of soldiers had overcome a much larger one, not by having a better position, or through any blunder of the enemy, but by the valor of the generals and the fighting quality of the army. Nicomedes now encamped alongside of Manius.
Mithridates ascended Mount Scoroba, which lies on the boundary between Bithynia and Pontus. A hundred Sarmatian horse of his advance-guard came upon 800 of the Nicomedean cavalry and took some of them prisoners.
Mithridates dismissed these also to their homes and furnished them supplies. Neoptolemus, and Nemanes the Armenian, overtook Manius on his retreat at the castle of Protophachium about the seventh hour, while Nicomedes was moving away to join Cassius, and compelled him to fight. He had 4,000 horse and ten times that number of foot. They killed 10,000 of his men and took 300 prisoners. When they were brought to Mithridates he released them in like manner, thus winning the good opinion of his enemies. The camp of Manius was also captured.
He fled to the river Sangarius, crossed it by night, and escaped to Pergamon. Cassius and Nicomedes and all the Roman ambassadors who were with the army decamped to a place called the Lion's Head, a very powerful stronghold in Phrygia, where they began to drill their newly collected mob of artisans, rustics, and other raw recruits, and made new levies among the Phrygians.
Finding them worthless, they abandoned the idea of fighting with such unwarlike men, dismissed them and retreated; Cassius with his own army to Apamea, Nicomedes to Pergamon, and Manius toward Rhodes. When those who were guarding the mouth of the Euxine learned these facts they scattered also and delivered the straits and all the ships they had to Mithridates.
 Having subverted the whole dominion of Nicomedes at one blow, Mithridates took possession of it and put the cities in order. Then he invaded Phrygia and lodged at an inn which had been occupied by Alexander the Great, thinking that it would bring him luck to halt where Alexander had once stopped.
He overran the rest of Phrygia, together with Mysia and those parts of Asia which had been lately acquired by the Romans. Then he sent his officers to the adjoining provinces and subjugated Lycia, Pamphylia, and the rest as far as Ionia. To the Laodiceans on the river Lycus, who were still resisting (for the Roman general, Quintus Oppius, had arrived with his cavalry and certain mercenaries at their town and was defending it), he made this proclamation by herald before the walls, "King Mithridates promises that the Laodiceans shall suffer no injury if they will deliver Oppius to him."
Upon this announcement they dismissed the mercenaries unharmed, but led Oppius himself to Mithridates with his lictors marching in front of him by way of ridicule. Mithridates did him no harm, but took him around with him unbound, exhibiting a Roman general as his prisoner.