While Mithridates was occupied fighting the Roman Republic, his ally and son-in-law, Tigranes II of Armenia, focused his efforts in other directions. The terms of the alliance between the two kings were basically that Tigranes would expand to the east and Mithridates to the west. Thus, the two states of Pontus and Armenia would defend against Rome and Parthia, respectively. Where Mithridates met defeat, however, Tigranes would enjoy much success.
|Coin depicting Tigranes the Great|
Tigranes ascended to the throne of Armenia in 658 AUC (96 BC), having been a hostage of the Parthian court until that time. He ceded much of Atropatene (Azerbaijan) to Mithridates II of Parthia, in return for being allowed to return to his homeland to rule. He quickly set about centralizing his rule and bringing the the feudal lords of Armenia under his control. Tigranes also began construction of a new capital for Armenia, named Tigranocerta.
As he solidified his rule over Armenia, Tigranes began to expand his influence. To the north, he secured Armenia's borders, placing a candidate of his own choosing on the Albanian throne after a brief succession crises in the small Caucasian state. He also induced the king of Iberia, Artaxias, who happened to be Armenian, into submission. By 664 AUC (90 BC), the northern border was secure and the state was firmly under his control.
It was in 665 AUC (89 BC) that an excellent opportunity presented itself to Tigranes. The Parthian king, Mithridates II, who has placed Tigranes on his throne, had just died. The Parthians immediately took to squabbling over the throne, the main contenders being Gotarzes, Orodes, Sinatruces, and Phraates. Further, Parthia was facing increasing pressure from Scythian nomads, further weakening the empire.
With a mixed infantry and cavalry army, Tigranes descended upon the Parthians, quickly reclaiming the territory he had ceded them in Atropatene. He met a relatively large force along the Tigris river, near Arbela, and defeated it utterly. He continued to march down through Mesopotamia, reaching the Parthian capital of Ctesiphon and capturing it. He also, while occupying the city, was heralded as a liberator by the Greeks in nearby Seleucia.
It was while he was campaigning in that area that the Romans were finally victorious over Mithridates. Concerned at being exposed to invasion by the Rome, he sent envoys to the Republic, proclaiming his friendship. He also claimed that his wife, Cleopatra, Mithridates daughter, had recently been discovered to being involved in an affair while he was on campaign. He ended his marriage with her and handed her over to the Romans as part of Mithridates' family. Whether or not the accusation was true, or was invented by Tigranes to justify handing over his wife, it cannot be certain. However, she had yet to bear him any son that had lived beyond a young age, and only one daughter, so it is not inconceivable that he was looking for a new wife. Whatever the case may be, the Republic, not entirely eager for a new war with such an illustrious general, seemed placated by his envoys, and accepted his friendship.
With relations with the Romans stable for the time being, Tigranes redoubled his efforts against the Parthians, and eventually reached Ecbatana. The Parthian vassals, most notably that of Persia, began to rise up against their overlords, heartened by Tigranes' victories. The Parthian kingdom seemed to be on its last legs. However, as Tigranes campaigned, particularly while away from the easy transport available in Mesopotamia, his supply lines became more and more vulnerable. Further, Roman sentiment was not amicable to his total domination of Parthia, further jeopardizing Tigranes' conquest.
Mindful of the risks he faced, Tigranes slowed his campaign and treated with the Parthians in 667 AUC (87 BC). He would ally himself to whichever claimant was willing to recognize his conquest of northern Mesopotamia and all of Atropatene and the independence of Persia, Characene, and Elymais. It would be Phraates, styling himself Phraates III, who first accepted Tigranes offer. With Armenian support, Phraates quickly solidified his position and defeated his rival claimants, marrying his sister off to the now single Tigranes.
Thus, Tigranes had expanded Armenia greatly at the expense of Parthia, which still retained it Iranian core and the central region of Mesopotamia. Tigranes then topped off his defeat of Parthia by being invited to take the crown of Syria, where the locals had grown tired of the waning Seleucids. This campaign was short, taking less than a year. By 669 AUC (85 BC), Tigranes' empire stretched from the Mediterranean in the west, the Caspian in the east, the Caucasus in the north, and down into Mesopotamia in the south.
Having conquered so much, he spent much of the rest of his reign consolidating his holdings, having the most success in the mountainous regions to the north, where the locals were most closely related to the Armenians. Tigranes, now deservedly called 'The Great', styled himself 'King of Kings' and was attended by various kings under him at all times. Not even the Parthian kings could claim such prestige at that time, particularly having lost most of their vassal states. Tigranes' most daunting task lay in holding at bay Roman expansionist designs, a task to which he had mixed success.
Once more, the basic outline of this piece of history is not radically different from the events of our history. Largely, dates have been altered by a year or two in many cases. The most radical changes come from the early defeat and capture of Mithridates. In our history, Tigranes provided refuge to the Pontic king after he was finally defeated, decades later. This invited invasion from Rome, and Tigranes' conquests were largely undone, his eponymous capital razed, and Armenia reduced to a client state.
However, with Mithridates a captive in Rome, Tigranes is free to weasel his way out of conflict with Rome. I also changed the progeny of his marriage to Cleopatra, to make it easier for him to betray her to Rome. With conflict with Rome delayed for the time being, Tigranes is able to expand upon his conquests in Parthia, nearly crippling the Arsacid dynasty.