As heirs to the Hellenistic world and empire builders themselves, the Romans had a particular interest in Alexander's conquests. By studying Alexander and his world, the Romans gained insight into the political and cultural dimensions of their own expansion. When the Roman historian Polybius set out to trace the history of the Second Punic War, a key conflict in Rome's struggle with Carthage for domination of the Mediterranean, he found it useful to employ Alexander's conquest of Persia as an example of his theory of historical causation. While his focus was on this theory, Polybius was clearly implying that the same kinds of explanations he offered for Macedonian expansion could and should be sought for Roman expansion. Crucially, his explanation centered not on a divine mandate or the inherent superiority of Greek culture, but rather on practical considerations and the political and economic dimensions of an attack on Persia. As you read this excerpt from Polybius's Histories, consider what it tells us about how Polybius saw Alexander's conquests and what connections he might have made between Alexander's world and his own.

I might concede that these events constitute the beginnings of the [Second Punic] War, but I cannot agree that they are its causes. One might just as well say that the crossing of Alexander into Asia was the cause of the Persian war, and the landing of Antiochus [III] at Demetrias was the cause of his war with Rome, neither of which statements would be plausible or true. No one could call these actions the causes of these wars—in the first case many preparations and plans for the Persian war had been made earlier by Alexander, and some even by his father Philip when he was alive, and similarly in the second case by the Aetolians even before the arrival of Antiochus. Such terminology is used by those who cannot grasp how great is the distinction between a beginning, a cause, and a pretext, and who fail to see that a cause is the first in a sequence of events of which the beginning is the last. My view is that the word beginning should refer to the first attempt to carry out a plan that has already been decided upon, and the word cause to the events which influence in advance our purposes and decisions. By this I mean the intentions, dispositions and calculations which lead us to make decisions and form plans. All this is illustrated by the instances I mentioned above. Anyone can easily recognize the true causes and origins of the war against the Persians. The first was the return march of the Greeks under Xenophon through the upper satrapies, in the course of which they traversed the whole of Asia, but none of the barbarians dared to face them though they were in hostile territory. The second was the invasion of Asia by the Spartan king Agesilaus, in which he did not meet any serious opposition to his incursions, though he was compelled by disturbances in Greece to abandon his project and return home. All this convinced Philip of the cowardice and indolence of the Persians, as against his own and the Macedonians efficiency in war. He could also see the magnitude and splendour of the rewards that could be expected from the war, and the popularity it would bring him from the Greeks. He therefore seized the pretext of avenging the injuries inflicted on the Greeks by the Persians, and devoted all his energies to making intensive preparations for the war. We must therefore consider the events mentioned first to be the cause of the war against the Persians, the pretext came second, and the beginning of the war was marked by Alexander's crossing into Asia.

Source: M. M. Austin, ed., The Hellenistic World from Alexander to the Roman Conquest: A Selection of Ancient Sources in Translation, 2d augmented ed. (New York: Cambridge University Press, 2006), pp. 23–24.

QUESTIONS TO CONSIDER