In 163, while Statius Priscus was occupied in Armenia, the Parthians invaded Osroene, a Roman client state in upper Mesopotamia, just east of Syria, with its capital at Edessa. They deposed the country's leader, Mannus, and replaced him with their own nominee, who would remain in office until 165. In response, Roman forces were moved downstream, to cross the Euphrates at a more southerly point. The Parthians still held the southern, Roman bank of the Euphrates (in Syria) as late as 163. Before the end of the year, however, Roman forces had moved north to occupy Dausara and Nicephorium on the northern, Parthian bank. Soon after the conquest of the north bank of the Euphrates, other Roman forces moved on Osroene from Armenia, taking Anthemusia, a town south-west of Edessa. There was little movement in 164; most of the year was spent on preparations for a renewed assault on Parthian territory.