Arrian was able to use sources which are now lost, such as the contemporary works by Callisthenes (the nephew of Alexander's tutor Aristotle), Onesicritus, Nearchus, and Aristobulus, and the slightly later work of Cleitarchus.
He is next heard of in the winter of 114/115, during Trajan’s Parthian war, commanding Legio VI Ferrata, which according to a fragment of the Parthica of Arrian he marched in deep snow (having secured snowshoes from native guides) across the Armenian Taurus to get to Tigranakert.
Arrian cites Ptolemy as saying Cyropolis surrendered from the start, and Arrian also states that according to Aristobulus the place was stormed and everyone was massacred.
According to Arrian (Anabasis, 29), he built a city on the spot whence he started to cross the river Hydaspes, which he named Bukephala or Bucephala to honour his famous and loyal horse Bukephalus or Bucephalus.
At least he is termed by Arrian satrap of Parthia, during the advance of Alexander against Bessus, when he was detached by the king, together with Erigyius and Caranus to crush the revolt of Satibarzanes, in Aria (329 BC).
His name appears twice in Arrian's Anabasis and once in Historiae Alexendri Magni by Curtius.
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Saśigupta (Arrian Sisikottos; Curtius Sisocostus) was an historical personage of considerable eminence hailing from the Paropamisadaen region i.e. region lying between Hindukush and Indus.
According to Arrian, upon this, he sent a force against him, led by Artabazus, Erigyius, and Caranus.
In 1797 he issued his commentary on Arrian's Voyage of Nearchus (contained in the Indica), which he terms ‘the first event of general importance to mankind in the history of navigation’.