Therefore, seminal information is preserved by writers of universal history, starting off with Diodorus. He was born in Sicily and after the middle of the first century BCE he went to Rome and published the result of his comprehensive studies, the Bibliotheke (40 books). Parts of this opus have been preserved completely (1–5; 11–20) and some only in fragments. The history of the Persian Empire was treated according to the perspectives of Greek history both from a thematic and from a chronological point of view. Book 17 contains the earliest history of Alexander the Great so far preserved (with a gap concerning the period from 329 to 327 BCE), mainly based on the Vulgate. Herodotus, Ctesias, and Ephorus were the central sources for Diodorus' view of the Persian Empire before Alexander's campaign. His work is of utmost importance for our knowledge of the relationship and the conflicts between Greece and Persia in the fourth century BCE (Stronk 2017).
Dating back to Byzantine times only few excerpts of the large universal history by Nicolaus of Damascus, written in the time of Augustus, have come down to us. They present a fantastical history of Cyrus which was based on Ctesias. Of greater importance was another work of universal history, written in Latin by Pompeius Trogus, a native of Gallia Narbonensis. His 44 books are preserved only by an excerpt made by Iustinus (Epitome), which was probably written in the third century CE. The story of the Persian kings ranging from Cyrus to Darius I is mainly based on Herodotus, but additions based on later writers such as Ctesias were also made. The accounts of the reigns of Artaxerxes II and Artaxerxes III are of great importance. Books 11–12 treating the wars of Alexander the Great are strongly influenced by the Vulgate, although the author's own critical views also become obvious. Along with Herodotus' work, Justinus became the main source for the description of the Persian Empire and its history in the Historiae Adversus Paganos by Orosius of Bracara, which is considered the most salient work of Christian universal history of late antiquity (Rollinger 2011).
Biographies, which began to become more popular, also played an essential role for the development of elementary ideas regarding the Persian Empire and its protagonists. The Vitae by Cornelius Nepos dating back to the later Roman Republic include a series of Greek army leaders who had to deal with representatives of the Persian Empire. The image of the Persian Empire is conventional, but Nepos also conveys some important information originating from sources of the fourth and fifth centuries BCE which have been lost in the original. His Datames, mainly based on Dinon's Persica, whom Nepos greatly admired (c.f. Konon 5.4), is of outstanding importance. Datames represents a noble satrap who fell victim to a false friend (Mithridates) and is destroyed by the hatred of the Great King (Artaxerxes II).
Even more than Nepos' Vitae, Plutarch's comprehensive biographies include important details on the relationship between Greek communities and the Persian Empire, which often date back to the fourth and fifth centuries BCE. His Alexander gained exceptional importance. It gives an idealized image of the protagonist and presents a series of interesting anecdotes. The Persian Empire itself is regarded more as a background setting for the story. The biography of Artaxerxes II requires special mention. The author mainly draws on information from the lost Persica by Ctesias and Dinon, giving a somewhat questionable image of the king living in a court full of luxury and intrigues (Binder 2008).
Plutarch's Moralia, a series of different essays, offer further, more scattered information about Persian customs and institutions, a number of anecdotes, and even details on Persian religious beliefs. The dominating point of view is determined by Greek ideas on moral behavior and cultural values. It also becomes obvious that Plutarch's attitude toward the conflicts between Greeks and Persians is far from neutral. In his treatise De malignitate Herodoti he addresses Herodotus' sympathy for the Barbarians in a negative way. A perfect example of the rhetorical idealization of Alexander is an early treatise where Plutarch addresses the idea of uniting the peoples of Asia and Europe by Alexander, who makes them live under the same order and rule (De Alexandri magni fortuna aut virtute, libri ii = Moralia 32d–34b).
The two most outstanding treaties on Alexander also appeared within the first two centuries CE. Curtius wrote a Historia Alexandri Magni in 10 volumes, of which 3–10 are still preserved, although with some lacunae. Based on the Vulgate, Curtius gives a fascinating account that includes a series of dramatic scenes and harsh moral judgments which point to the author's contemporary society. Alexander, a highly talented young king whose incredible success is too great a challenge for his moral competence, develops into a tyrannical ruler (Wulfram 2016). Meanwhile, Darius III is presented as a more respectable character; however, the “oriental” setting of the story is described fascinatingly but in a cliché way. The Macedonian habit of taking on Persian customs and Persian luxury is evaluated in an extremely negative way by Curtius. He even mentions a melting together of the vices of both peoples (9.7.15) (Rollinger 2009; Briant 2010).
The image of Alexander put forth by Arrian is entirely different. The author from Nicomedia possibly already outlined his work under the influence of Trajan's campaign against the Parthians and then completed it in the course of the decades that followed. He described Alexander's campaigns in seven books, which he called Anabasis (as with Xenophon whose example he had taken). This work is followed by a small Indike. Although Arrian's Alexander also shows some negative traits, he mostly behaves in a very competent way, especially with regard to his strategic abilities. Ptolemy's work may have helped Arrian in describing the military ventures – both the big battles and the wearing feuds in the upper satrapies as well as the brutal campaign in India – as undertakings that worked according to a rigid order. The cultural world of the Achaemenid Empire remains relatively obscure to Arrian. But his Anabasis is one of the most important sources concerning the topography, the infrastructure, and the administration of the Persian Empire (Bosworth 1980, 1995; Ruffing 2017).
Strabo's Geography is also an important source of information regarding these issues. In his work, which comprises 17 volumes, Strabo places the Imperium Romanum under the reign of the Emperor Augustus in the center of the oikumene. Geography is full of allusions to Alexander's campaign as well as to the deeds of the former Persian kings from Cyrus to Xerxes. Strabo's work gives detailed geographical accounts of the regions that had once been ruled by the Achaemenids and it includes a series of fragments of the early Alexander‐historians. The encyclopedia (Naturalis historia) by Pliny the Elder (first century CE) abounds with details on the geography and nature of the Persian Empire. Claudius Ptolemy (second century CE) wrote a geographical handbook that preserves the whole contemporary cartographic knowledge of his time, including those regions where the Achaemenids once lived and ruled (Lenfant 2017).
On the whole, the importance of the literature written under Roman rule during the first centuries CE can hardly be overestimated regarding the understanding of what was said to be known about the Achaemenid Empire in Greek and Roman antiquity. As Lucius Ampelius states in his liber memorialis, a basic knowledge of the Achaemenid Empire was part of the elementary educational program (c. 13). The personality of the rulers and sometimes also that of generals as well as of noble women was a constant source of examples of exemplary and deterring behavior. Such examples are to be found in the writings by Valerius Maximus (first century CE) and in the anecdotes by Aelian (second/third century CE). According to Aelian, Artaxerxes III who conquered Egypt once again was regarded as a sacrilegious despot like Cambyses (varia historia 4.8; 6.8; natura animalium 28). Athenaeus (second century CE) gives account of the way Persian luxury was imagined at the court of the Great King. So he describes that according to Heracleides Ponticus, the Persians and the Medes loved luxury