Please note that Mommsen uses the AUC chronology (Ab Urbe Condita), i.e. from the founding of the City of Rome. You can use this reference table to have the B.C. dates
From: The History of Rome, by Theodor Mommsen
Translated with the sanction of the author by William Purdie Dickson
Lucullus Advances into Armenia
But while the troublesome temper of the government and of the soldier thus threatened the victorious general with recall and mutiny, he himself continued like a desperate gambler to increase his stake and his risk. 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.
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Reference address : https://www.ellopos.net/elpenor/rome/5-02-rule-sullan-restoration.asp?pg=54