Balāš III, king from 129 to 146/8 (according to Le Rider; cf. Hanslik, col. 1847, under Vologaeses II). The struggle between Osroes and Balāš III appears to have continued after, perhaps even during, Trajan’s Parthian war. Balāš III finally prevailed in 127/8 or in any case not later than 129. The minting of coins of Osroes at Seleucia cease from 127/8 onward, but Osroes is known to have met the emperor Hadrian during the latter’s tour of the East in 129 and to have obtained the release of his daughter, whom the Romans had captured in 116.

Balāš III soon came up against the usual “Parthian problem” of a pretender’s revolt. This particular counter-king, Mithridates IV, seems only to have controlled provinces on the Iranian plateau (Debevoise, p. 244 n. 15; Sellwood, p. 262). Roman-Parthian relations having been trouble-free in the first part of Balāš III’s reign, and the Roman historians being uninterested in Parthia’s internal affairs, information about the course of events is lacking. All that can be said is that Mithridates’s venture did not bring him any lasting success.

A much graver threat to Balāš III’s rule came from the invasion by Alan nomads in the years 134-36. They penetrated into Albania, Media, Armenia, and also Cappadocia, and were only driven out with great difficulty and doubtless heavy financial expense. In the reign of Hadrian’s successor Antoninus Pius (138-61), trouble over Armenia again flared up, but details of the events, which probably took place between 140 and 144, are lacking. All that is known is that the Romans installed a new king in Armenia. Balāš III made no countermove, either because he did not feel strong enough or perhaps because he did not wish to endanger the flourishing long-distance trade, from which the Parthians drew large profits (see Chaumont, pp. 146-47; Ziegler, pp. 110-11).