Traiana Nova) was built from Aila (now Aqaba) in Limes Arabicus to Bosrah. As Nabataea was the last client kingdom in Asia west of the Euphrates, the annexation meant that the entire Roman East had been provincialized, completing a trend towards direct rule that had begun under the Flavians. Parthian campaign In 113, Trajan embarked on his last campaign, provoked by Parthia's decision to put an unacceptable king on the throne of Armenia, a kingdom over which the two great empires had shared hegemony since the time of Nero some fifty years earlier. Trajan, already in Syria early in 113, consistently refused to accept diplomatic approaches from the Parthians intended to settle the Armenian imbroglio peacefully. As the surviving literary accounts of Trajan's Parthian War are fragmentary and scattered, it is difficult to assign them a proper context, something that has led to a long-running controversy about its precise happenings and ultimate aims. Cause of the war Modern historians advance the possibility that Trajan's decision to wage war against Parthia had economic motives: after Trajan's annexation of Arabia, he built a new road, Via Traiana Nova, that went from Bostra to Aila on the Red Sea. That meant that Charax on the Persian Gulf was the sole remaining western terminus of the Indian trade route outside direct Roman control, and such control was important in order to lower import prices and to limit the supposed drain of precious metals created by the deficit in Roman trade with the Far East. That Charax traded with the Roman Empire, there can be no doubt, as its actual connections with merchants from Palmyra during the period are well documented in a contemporary Palmyrene epigraph, which tells of various Palmyrene citizens honoured for holding office in Charax. Also, Charax's rulers domains at the time possibly included the Bahrain islands, which offered the possibility of extending Roman hegemony into the Persian Gulf itself. (A Palmyrene citizen held office as satrap over the islands shortly after Trajan's death, though the appointment was made by a Parthian king of Charax.) The rationale behind Trajan's campaign, in this case, was one of breaking down a system of Far Eastern trade through small Semitic ("Arab") cities under Parthia's control and to put it under Roman control instead. In his Dacian conquests, Trajan had already resorted to Syrian auxiliary units, whose veterans, along with Syrian traders, had an important role