his war against the two monarchs initially, their forces remained a threat to the Romans and still possessed the strength to repel him. Phraates III seemingly made promises to both parties but remained passive to await the outcome of the war. He could then take advantage of it at the right moment for the Parthians. In 66 BC, Phraates III entered into negotiations with Lucullus' successor Pompey, who possibly offered Roman acknowledgement of Parthian authority over Mesopotamia, Adiabene, and Gordyene in exchange for military aid. Around the same time, Tigranes' namesake son and heir, Tigranes the Younger, fell out with his father and fled to the court of Phraates III. He agreed to help Phraates III take the Armenian throne in return for marrying his daughter. This marriage, which took place in 66/65 BC, gave Phraates III the opportunity to involve himself in the affairs of Armenia, including preventing Pompey from putting Parthian interests in jeopardy. Phraates III, together with Tigranes the Younger, led an expedition into Armenia. Initially successful, their efforts were halted by a long siege at Artaxata, which led Phraates III to put Tigranes the Younger in charge of the Armenian expedition, reinforcing him with some Parthian soldiers. Ultimately, Tigranes the Younger was defeated by his father, however, leading him to desert Phraates III and join Pompey instead. Tigranes the Elder soon surrendered to Pompey, who chose to allow him to retain his crown. Instead, Tigranes the Younger was made the ruler of Sophene with the assurance that he would ascend to the Armenian throne after his father's death. However, after a brief reign, Tigranes the Younger was imprisoned and deported to Rome. The reason behind this is disputed. According to Rahim M. Shayegan, it was because he remained an ally of Phraates III, with whom he still conspired with to overthrow Tigranes the Elder, whilst Michał Marciak states it was due to his dispute with Pompey over Sophene's treasury. In the spring of 65 BC, Phraates III protested the arrest of his son-in-law but to no avail. Around the same time—in late 65 BC—Phraates III reconquered Adiabene, Gordyene and northern Mesopotamia. However, a Roman attack under the generals Aulus Gabinius and Lucius Afranius as far as the Tigris resulted in Phraates III losing Gordyene, which was restored to Tigranes by the Romans. Phraates III protested against the Romans for the second time—again to no avail. After