But far worse than all this military and financial perplexity was the reaction of the political revolution in Rome; the rapid, sweeping, violent accomplishment of which had far surpassed the worst apprehensions. The revolution conducted the government in the capital; Sulla had been deposed, his Asiatic command had been entrusted to the democratic consul Lucius Valerius Flaccus, who might be daily looked for in Greece. The soldiers had no doubt adhered to Sulla, who made every effort to keep them in good humour; but what could be expected, when money and supplies were wanting, when the general was deposed and proscribed, when his successor was on the way, and, in addition to all this, the war against the tough antagonist who commanded the sea was protracted without prospect of a close?
King Mithradates undertook to deliver his antagonist from his perilous position. He it was, to all appearance, who disapproved the defensive system of his generals and sent orders to them to vanquish the enemy with the utmost speed. As early as 667 his son Ariarathes had started from Macedonia to combat Sulla in Greece proper; only the sudden death, which overtook the prince on the march at the Tisaean promontory in Thessaly, had at that time led to the abandonment of the expedition. His successor Taxiles now appeared (668), driving before him the Roman corps stationed in Thessaly, with an army of, it is said, 100,000 infantry and 10,000 cavalry at Thermopylae. Dromichaetes joined him. Archelaus also - compelled, apparently, not so much by Sulla's arms as by his master's orders - evacuated the Piraeeus first partially and then entirely, and joined the Pontic main army in Boeotia. Sulla, after the Piraeeus with all its greatly-admired fortifications had been by his orders destroyed, followed the Pontic army, in the hope of being able to fight a pitched battle before the arrival of Flaccus. In vain Archelaus advised that they should avoid such a battle, but should keep the sea and the coast occupied and the enemy in suspense. Now just as formerly under Darius and Antiochus, the masses of the Orientals, like animals terrified in the midst of a fire, flung themselves hastily and blindly into battle; and did so on this occasion more foolishly than ever, since the Asiatics might perhaps have needed to wait but a few months in order to be the spectators of a battle between Sulla and Flaccus.
In the plain of the Cephissus not far from Chaeronea, in March 668, the armies met. Even including the division driven back from Thessaly, which had succeeded in accomplishing its junction with the Roman main army, and including the Greek contingents, the Roman army found itself opposed to a foe three times as strong and particularly to a cavalry fur superior and from the nature of the field of battle very dangerous, against which Sulla found it necessary to protect his flanks by digging trenches, while in front he caused a chain of palisades to be introduced between his first and second lines for protection against the enemy's war-chariots. When the war chariots rolled on to open the battle, the first line of the Romans withdrew behind this row of stakes: the chariots, rebounding from it and scared by the Roman slingers and archers, threw themselves on their own line and carried confusion both into the Macedonian phalanx and into the corps of the Italian refugees. Archelaus brought up in haste his cavalry from both flanks and sent it to engage the enemy, with a view to gain time for rearranging his infantry; it charged with great fury and broke through the Roman ranks; but the Roman infantry rapidly formed in close masses and courageously withstood the horsemen assailing them on every side. Meanwhile Sulla himself on the right wing led his cavalry against the exposed flank of the enemy; the Asiatic infantry gave way before it was even properly engaged, and its giving way carried confusion also into the masses of the cavalry. A general attack of the Roman infantry, which through the wavering demeanour of the hostile cavalry gained time to breathe, decided the victory. The closing of the gates of the camp which Archelaus ordered to check the flight, only increased the slaughter, and when the gates at length were opened, the Romans entered at the same time with the Asiatics. It is said that Archelaus brought not a twelfth part of his force in safety to Chalcis; Sulla followed him to the Euripus; he was not in a position to cross that narrow arm of the sea.
It was a great victory, but the results were trifling, partly because of the want of a fleet, partly because the Roman conqueror, instead of pursuing the vanquished, was under the necessity in the first instance of protecting himself against his own countrymen.
The sea was still exclusively covered by Pontic squadrons, which now showed themselves even to the westward of the Malean promontory; even after the battle of Chaeronea Archelaus landed troops on Zacynthus and made an attempt to establish himself on that island. Moreover Lucius Flaccus had in the meanwhile actually landed with two legions in Epirus, not without having sustained severe loss on the way from storms and from the war-vessels of the enemy cruising in the Adriatic; his troops were already in Thessaly; thither Sulla had in the first instance to turn. The two Roman armies encamped over against each other at Melitaea on the northern slope of Mount Othrys; a collision seemed inevitable. But Flaccus, after he had opportunity of convincing himself that Sulla's soldiers were by no means inclined to betray their victorious leader to the totally unknown democratic commander-in chief, but that on the contrary his own advanced guard began to desert to Sulla's camp, evaded a conflict to which he was in no respect equal, and set out towards the north, with the view of getting through Macedonia and Thrace to Asia and there paving the way for further results by subduing Mithradates. That Sulla should have allowed his weaker opponent to depart without hindrance, and instead of following him should have returned to Athens, where he seems to have passed the winter of 668-9, is in a military point of view surprising. We may suppose perhaps that in this also he was guided by political motives, and that he was sufficiently moderate and patriotic in his views willingly to forgo a victory over his countrymen, at least so long as they had still the Asiatics to deal with, and to find the most tolerable solution of the unhappy dilemma in allowing the armies of the revolution in Asia and of the oligarchy in Europe to fight against the common foe.
In the spring of 669 there was again fresh work in Europe. Mithradates, who continued his preparations indefatigably in Asia Minor, had sent an army not much less than that which had been extirpated at Chaeronea, under Dorylaus to Euboea; thence it had, after a junction with the remains of the army of Archelaus, passed over the Euripus to Boeotia. The Pontic king, who judged of what his army could do by the standard of victories over the Bithynian and Cappadocian militia, did not understand the unfavourable turn which things had taken in Europe; the circles of the courtiers were already whispering as to the treason of Archelaus; peremptory orders were issued to fight a second battle at once with the new army, and not to fail on this occasion to annihilate the Romans. The master's will was carried out, if not in conquering, at least in fighting.