The article below by M. L. Chaumont on “Ammianus Marcellinus” on the Encyclopedia Iranica was originally published on December 15, 1989 and last updated on August 3, 2011. This article is also available in print (Vol. I, Fasc. 9, pp. 977-979). Kindly note that the images and accompanying captions do not appear in the original Encyclopedia Iranica article.
Ammianus Marcellinus, historian who provides important information on the Sasanians. Born ca. 330-35 in Antioch on the Orontes to a wealthy family of Greek origin, he received a bilingual education in Greek and Latin. Toward 350 he entered the elite group of the protectores domestici and was appointed to the staff of the general Ursicinus. He took part in the Roman Mesopotamian campaign and in the operations at Amida in 359; four years later, he accompanied the Emperor Julian on his disastrous expedition against the Persians. Following these events, he abandoned his military career and retired to Antioch. Toward 380, after having traveled in Egypt and Greece, he settled in Rome, where he composed his historical work in Latin. He was still alive in 392; it is thought that he died ca. 395. He calls himself Graecus (31.16.9) but, shaped at an early age by the army, he was acting as a typical Roman. In religion, he was pagan. His Res Gestae originally consisted of thirty-nine books; the first thirteen, which covered the period from 93 to 353 A.D., including the Parthian Wars, have disappeared. The remaining books covering the period from 353 to 378, are important for the history of the Sasanian empire in the 4th century. The author expresses himself in the obscure and labored Latin typical of the late empire.
Cover page of text by Greco-Roman historian Ammianus Marcellinus published in Augsburg in 1533 (Source: Photograph by Feldkurat Katz in Public Domain).
Ammianus was solidly prejudiced against the Persians, whom he considered the hereditary enemies of the Roman Empire. Though he did not know their language, he provides abundant and valuable information on the history of the reign of Šāpūr II, particularly between 353 and 363. As a protector, he was in a good position to obtain first-hand information, whether through conversations with Ursicinus and other military personalities, or through staff reports based on statements of scouts, spies, or deserters. He seems to have received information on the Persian-Roman negotiations of 354-63 from those actually involved. He shows himself equally well informed about the bodyguard Antonius, who went over to the enemy camp, received from Šāpūr the honor of wearing a tiara, and eventually became his mentor (Res Gestae 17.5.1-3, 6-8; 6.3). Ammianus had access to official documents, e.g., the famous letter of Šāpūr II to Constantine (17.5.3-9). In 539 he was sent to contact Iovinianus, the Sasanian satrap of Gordyene, and during this mission he could see from a mountaintop the Persian troops proceeding toward Amida (18.6.21-22). Then he personally participated in the defense of Amida when it was invested by the Persians (July-October, 359) and provides many first-hand accounts of the siege, which was to end in disaster for the Romans. He describes carefully the tactics of the Persians, their war machines (earthworks, high towers studded with iron spikes, etc.), their arms, which were so different from those of the Romans (suits of scale armor