shift of emphasis in the "grand strategy" of the empire. Finally, one characteristic of the Roman presence in Persia is that Roman emperors dreamed of conquering all Persia from Trajan to Galerius, while Parthian/Sassanian kings never tried to conquer Rome, Italy or southeastern Europe according to historian Theodor Mommsen. Roman Parthia Romans were able to conquer the westernmost part of Parthia under emperor Trajan. Indeed, in 113 AD Trajan invaded Parthia, marching first on Armenia. In 114 AD Trajan annexed Armenia to the Roman empire, after defeating and killing Parthamasiris, relative of Osroes I of Parthia. Then he turned south into Parthia itself, taking the cities of Babylon, Seleucia and finally the capital of Ctesiphon in 116 AD. He deposed Osroes I and put his own puppet ruler Parthamaspates on the throne. In Mesopotamia Osroes' brother Mithridates IV and his son Sanatruces II took the diadem and fought against the Romans, but Trajan marched southward to the Persian Gulf, defeated them, and declared Mesopotamia a new province of the empire. In the process, he also captured the great city of Susa in Khuzestan. Those months of 116 and 117 saw western Parthia as a client state of the Romans. Trajan originally planned to annex Parthia as part of the Roman Empire, but ultimately decided instead to place Parthamaspates on his father's throne as a Roman client, doing so in 116. Trajan created even the province of Assyria, whose eastern border were never well defined by historians: it is possible that included northwestern Elam, a semi-autonomous Persian province (now Īlām Province of Iran) that welcomed his conquest of Mesopotamia. Following the death of Trajan and Roman withdrawal from the area, Osroes easily defeated Parthamaspates and reclaimed the Persian throne. Hadrian acknowledged this fait accompli, recognized Osroes, Parthamaspates king of Osroene, and returned Osroes' daughter who had been taken prisoner by Trajan (as a warranty to control his client state). Even if there were further attacks from Roman emperors against the Parthian and later Sassanid empire (Romans even suffered humiliating defeats, like with emperor Valerian), no huge territory of actual Iran was never occupied again by Roman legions: The Romans stopped always after conquering Ctesiphon and soon returned behind their "limes siriacus" (only in 298 AD western Atropene up to lake Urmia was occupied by Romans for half a century). Indeed, this city (capital of the Parthian and Sassanian empire, but not