He did not indeed march against the Parthians but when Tigranes showed himself neither ready to make peace nor disposed, as Lucullus wished, to risk a second pitched battle, Lucullus resolved to advance from Tigranocerta, through the difficult mountain-country along the eastern shore of the lake of Van, into the valley of the eastern Euphrates (or the Arsanias, now Myrad-Chai), and thence into that of the Araxes, where, on the northern slope of Ararat, lay Artaxata the capital of Armenia proper, with the hereditary castle and the harem of the king.
He hoped, by threatening the king's hereditary residence, to compel him to fight either on the way or at any rate before Artaxata.

It was inevitably necessary to leave behind a division at Tigranocerta; and, as the marching army could not possibly be further reduced, no course was left but to weaken the position in Pontus and to summon troops thence to Tigranocerta.

The main difficulty, however, was the shortness of the Armenian summer, so inconvenient for military enterprises.

On the tableland of Armenia, which lies 5000 feet and more above the level of the sea, the corn at Erzeroum only germinates in the beginning of June, and the winter sets in with the harvest in September; Artaxata had to be reached and the campaign had to be ended in four months at the utmost.
At midsummer, 686, Lucullus set out from Tigranocerta, and, marching doubtless through the pass of Bitlis and farther to the westward along the lake of Van--arrived on the plateau of Musch and at the Euphrates.

The march went on--amidst constant and very troublesome skirmishing with the enemy's cavalry, and especially with the mounted archers--slowly, but without material hindrance; and the passage of the Euphrates, which was seriously defended by the Armenian cavalry, was secured by a successful engagement; the Armenian infantry showed itself, but the attempt to involve it in the conflict did not succeed.