Rome, though she had not yet determined on war with Mithridates, was resolved to thwart his Cappadocian projects, and in B.C.92 sent Sulla into Asia with orders to put down the puppet whom Mithridates and Tigranes were establishing, and to replace upon the Cappadocian throne a certain Ariobarzanes, whom they had driven from his kingdom.

In the execution of this commission, Sulla was brought into hostile collision with the Armenians, whom he defeated with great slaughter, and drove from Cappadocia together with their puppet king.
Thus, not only did the growing power of Mithridates of Pontus, by inspiring Rome and Parthia with a common fear, tend to draw them together, but the course of events had actually given them a common enemy in Tigranes of Armenia, who was equally obnoxious to both.
For Tigranes, who, during the time that he was a hostage in Parthia, had contracted engagements towards the Parthian monarch which involved a cession of territory, and who in consequence of his promises had been aided by the Parthians in seating himself on his father's throne though he made the cession required of him in the first instance had soon afterwards repented of his good faith, had gone to war with his benefactors, recovered the ceded territory, and laid waste a considerable tract of country lying within the admitted limits of the Parthian kingdom.

These proceedings had, of course, alienated Mithridates II.; and we may with much probability ascribe to them the step, which he now took, of sending an ambassador to Sulla.

Orobazus, the individual selected, was charged to propose an alliance offensive and defensive between the two countries.

Sulla received the overture favorably, but probably considered that it transcended his powers to conclude a treaty; and thus nothing more was effected by the embassy than the establishment of a good understanding between the two States.
Soon after this Tigranes appears to have renewed his attacks upon Parthia, which in the interval between B.C.92 and B.C.83 he greatly humbled, depriving it of the whole of Upper Mesopotamia, at this time called Gordyene, and under rule of one of the Parthian tributary kings.
Of the details of this war we have no account; and it is even uncertain whether it fell within the reign of Mithridates II.