Flavius Arrianus lived the better part of the 2nd century AD, born around 96 and died near 175 AD. He was governor of Cappadocia under Emperor Hadrian and in A.D. 134 repulsed an invasion of the Alans. His chief work is the Anabasis, the prime extant source on Alexander the Great.
The Anabasis relies chiefly on the writings of two of Alexander's generals (Ptolemy I and Aristobulus) for source material. Other extant works include the Indica (an account of a voyage of Alexander's general Nearchus to India).
His works on Alexander are some of the oldest surviving sources on the Macedonian conqueror.
Anabasis Alexandri (The Campaigns of Alexander)