In 53 B.C. Crassus and over 40,000 Roman troops were annihilated by the Parthian forces of Orodes II and the peoples from the Mediterranean to the Indus understood the strength of Parthia. But by 40 B.C. even Rome had to acknowledge a Parthia whose forces, under the joint command of Pacorus I and Q. Labienus, a Roman, had struck directly into the heart of the Roman East and captured the provinces of Asia, Pamphylia, Cilicia, and Syria; even as far south as Petra, Parthia's word was law. For two years this vast area, so vital to Roman interests, was under Parthian occupation. Possession of the Carian and perhaps the Ionian coast by foreigners struck close to home as many Romans were native to that part of the world or did business there. The occupiers were no sooner pushed out by Ventidius than another Roman army under Anthony was defeated and barely escaped annihilation at Parthian hands. [Debevoise, 208]

The tug of war with Rome on the western border of Parthia continued almost without cease while Parthia had to constantly see to other threats from the north and east. The western border between Rome's dominions and Parthia gradually stabilized on the banks of the Euphrates, but war was always a threat and though major campaigns by the Romans were seen in A.D. 116, 161, 195, 217 and 232, Parthia was never conquered.

и понеже си наясно с латинскя ето малко автори :
Principally Ammianus Marcellinus, Eutropius, Horace, Justin (Epitome of Pompeius Trogus), Orosius, Pliny the Elder, Quintus Dellius, Tacitus, Velleius Paterculus.

само с момзен не става.