Alexander announced himself before he had a kingdom: the boy who saw what Philip's horsemen could not and tamed Bucephalas, while his father, shedding tears of joy, told him to seek out a kingdom equal to himself — "Macedonia has not room for thee". Regent of Macedonia at sixteen, he plunged into the Granicus with thirteen troops of horsemen, took the tent of Dareius by the river Pinarus, and in Persis sat the royal throne itself — where old Demaratus the Corinthian wept for the Hellenes who had died too soon to see it. He died, Livy says, while still young, before fortune had time to turn.
Most of this file is carried by Plutarch, whose Alexander (c. 100 CE, written under Trajan; Bernadotte Perrin's translation, 1914–1926) weighs its own witnesses as it goes. At the Granicus twenty thousand of the enemy fall, yet Aristobulus, whom Plutarch cites, counts thirty-four dead on Alexander's side. Chares says Dareius himself dealt the sword-wound in the king's thigh; Alexander's own letter to Antipater names no one. Plutarch even corrects the shelf outright: the great battle against Dareius was "not fought at Arbela, as most writers state, but at Gaugamela" — the field where Alexander, pressed to attack by night, gave his celebrated answer, "I will not steal my victory".
Then the record argues back. Livy, Rome's historian (The History of Rome, c. 27 BCE–17 CE; Rev. Canon Roberts's translation, 1912), breaks his narrative for three full chapters to try a case no battlefield ever heard: "What would have been the results for Rome if she had been engaged in war with Alexander?" The concession comes first — "I do not dispute that Alexander was an exceptional general" — then the prosecution: the reputation is flattered by an early death; no man bore prosperity worse; had he marched west, "he would have come into Italy more like Darius than Alexander", his thirty thousand Macedonian veterans facing a people who had raised ten legions of city troops, and consul after consul his equal in courage and ability. Livy even names his opponents — Greeks so frivolous they extol the Parthians at Rome's expense. The Greek shelf celebrates the man; the Roman shelf cross-examines the celebration.
The two vantages never met in the field; Livy's war exists only on his own pages. The question the file leaves open: how would the record read if fortune had given the young king time to change?
Sources: Plut. Alexander 6 · Plut. Alexander 9 · Plut. Alexander 16 · Plut. Alexander 20 · Plut. Alexander 31 · Plut. Alexander 37 · Liv. 9.17 · Liv. 9.18 · Liv. 9.19