Such was the state in which Mithradates found matters, when his Macedonian phalanx crossing the ridge of the Caucasus descended into the valleys of the Kuban and Terek and his fleet at the same time appeared in the Crimean waters.  No wonder that here too, as had already been the case in Dioscurias, the Hellenes everywhere received the king of Pontus with open arms and regarded the half-Hellene and his Cappadocians armed in Greek fashion as their deliverers.  What Rome had here neglected, became apparent.  The demands on the rulers of Panticapaeum for tribute had just then been raised to an exorbitant height; the town of Chersonesus found itself hard pressed by Scilurus king of the Scythians dwelling in the peninsula and his fifty sons; the former were glad to surrender their hereditary lordship, and the latter their long-preserved freedom, in order to save their last possession, their Hellenism.  It was not in vain.  Mithradates’ brave generals, Diophantus and Neoptolemus, and his disciplined troops easily got the better of the peoples of the steppes.  Neoptolemus defeated them at the straits of Panticapaeum partly by water, partly in winter on the ice; Chersonesus was delivered, the strongholds of the Taurians were broken, and the possession of the peninsula was secured by judiciously constructed fortresses.  Diophantus marched against the Reuxinales or, as they were afterwards called, the Roxolani (between the Dnieper and Don) who came forward to the aid of the Taurians; 50,000 of them fled before his 6000 phalangites, and the Pontic arms penetrated as far as the Dnieper.(7) Thus Mithradates acquired here a second kingdom combined with that of Pontus and, like the latter, mainly based on a number of Greek commercial towns.  It was called the kingdom of the Bosporus; it embraced the modern Crimea with the opposite Asiatic promontory, and annually furnished to the royal chests and magazines 200 talents (48,000 pounds) and 270,000 bushels of grain.  The tribes of the steppe themselves from the north slope of the Caucasus to the mouth of the Danube entered, at least in great part, into relations of dependence on, or treaty with, the Pontic king and, if they furnished him with no other aid, afforded at any rate an inexhaustible field for recruiting his armies.

Lesser Armenia
Alliance with Tigranes

While thus the most important successes were gained towards the north, the king at the same time extended his dominions towards the east and the west.  The Lesser Armenia was annexed by him and converted from a dependent principality into an integral part of the Pontic kingdom; but still more important was the close connection which he formed with the king of the Greater Armenia.  He not only gave his daughter Cleopatra in marriage to Tigranes, but it was mainly through his support that Tigranes shook off the yoke of the Arsacids and took their place in Asia.  An agreement seems to have been made between the two to the effect that Tigranes should take in hand to occupy Syria and the interior of Asia, and Mithradates Asia Minor and the coasts of the Black Sea, under promise of mutual support; and it was beyond doubt the more active and capable Mithradates who brought about this agreement with a view to cover his rear and to secure a powerful ally.