Analyse the causes, key campaigns and consequences of Alexander's conquest of the Persian Empire (336 to 323 BCE), and evaluate the reliability of the surviving sources written centuries later.

What this dot point is asking

You must explain how and why Alexander conquered so rapidly, narrate the decisive campaigns, assess the consequences, and evaluate sources that are unusually distant from the events.

Causes: the inheritance from Philip

Alexander's conquests were built on foundations laid by his father, Philip II of Macedon, who reformed the army with the long pike (sarissa) and the disciplined phalanx, integrated cavalry, and unified Greece under Macedonian leadership in the League of Corinth. Philip planned an invasion of Persia, framed as revenge for the earlier Persian invasions of Greece, but was assassinated in 336 BCE. Alexander inherited a battle-ready professional army and the campaign already prepared, and added his own relentless drive.

The decisive campaigns

Crossing into Asia in 334 BCE, Alexander won at the river Granicus, then defeated the Persian king Darius III himself at Issus in 333 BCE. Rather than pursuing Darius at once, he secured the eastern Mediterranean coast, taking the great fortress city of Tyre after a famous siege and entering Egypt, where he founded Alexandria. He then met and crushed Darius' main army at Gaugamela in 331 BCE, opening the Persian heartland and the capitals of Babylon, Susa and Persepolis, the last of which was burned.

The eastern campaigns and the limit of conquest

Alexander pressed on into Central Asia and India, defeating the Indian king Porus at the Hydaspes in 326 BCE. There his exhausted troops refused to march further east at the river Hyphasis, and he turned back. The return through the Gedrosian desert cost many lives. He died at Babylon in 323 BCE, his sudden death amid plans for further campaigns leaving no settled succession.

Consequences

Alexander's empire did not survive him as a unit. His generals, the Diadochi, fought over the inheritance and carved out the great Hellenistic kingdoms. Yet the conquest spread Greek language, art and city-founding across the Near East for centuries, creating the Hellenistic world in which Greek culture mixed with Egyptian, Persian and Mesopotamian traditions, and through which much classical learning later reached Rome.

Evaluating the sources

The source problem is acute and central to any SACE study of Alexander. Eyewitnesses such as his officer Ptolemy and the engineer Aristobulus wrote accounts, but these are lost. Our surviving narratives, by Arrian, Plutarch, Diodorus, Curtius and Justin, were composed between roughly three and five centuries after Alexander, drawing on the lost earlier works. Arrian is usually rated most reliable because he followed Ptolemy and Aristobulus and wrote soberly, while others are more rhetorical or sensational. All wrote when Alexander had become a legend, so glorifying and moralising traditions shape every account.

Why this matters for your study

Alexander is a classic SACE military-conflict topic precisely because the brilliant narrative rests on such late evidence. Strong responses use accurate dates and battles while constantly noting that our sources are centuries removed and depend on lost originals, and they distinguish the more careful Arrian from the more colourful tradition.