Alexander the Great's military campaigns

Alexander the Great is one of the most charismatic and famous personalities of the Ancient world. He was only 20 years old when he came to power. As a result of Alexander the Great's campaign to the East, a new powerful state emerged that stretched from the Aegean Sea to the Indus River basin and from the Libyan desert to the Caspian Sea.

Background

The campaign against the Achaemenids was prepared by the strengthening of Macedonia under Philip II. Philip, not Alexander, established the Corinthian League after his victory at Chaeronea in 338 BC. Alexander inherited its leadership after his father’s death in 336 BC. The official theme of vengeance for the Persian Wars coexisted with the Macedonian monarchy’s interests and expansion of power.

The Persian Empire was not doomed in advance, and its army cannot be described by one permanent numerical strength. Its forces included cavalry, infantry and Greek mercenaries, with resources varying between campaigns. Alexander relied on the Macedonian phalanx, cavalry, light infantry and allied contingents. Ancient authors give different army totals; these estimates require comparison rather than literal acceptance.

Crossing the Hellespont in 334 BC opened the struggle for Asia Minor. Control of coastal cities and Persian naval bases mattered as well as field battles. The proclaimed liberation of Greek poleis coexisted with the establishment of Macedonian control.

Alexander the Great's military campaign to the East

Principal stages of the conquest:

• 334 BC — victory at the Granicus over Persian satrapal forces. Some cities of Asia Minor submitted; others had to be besieged.
• 333 BC — victory at Issus over Darius III. This was a major turning point, not the immediate conquest of the whole empire.
• 332 BC — sieges of Tyre and Gaza, followed by the occupation of Egypt. These operations secured much of the eastern Mediterranean coast.
• 331 BC — victory at Gaugamela and occupation of Babylon and Susa.
• 330 BC — occupation of Persepolis and further pursuit of Darius III. The king was killed by conspirators; Alexander continued fighting Bessus and other opponents.

Darius III commanded diverse forces, not an inherently ineffective army. Explaining the outcome solely through his supposed timidity or lack of infantry is incorrect. Macedonian organisation, manoeuvre, supplies, commanders’ decisions and political relations within conquered regions all mattered.

In 329–327 BC Alexander fought in Bactria and Sogdiana. Resistance, mobile enemy forces and difficult terrain made these campaigns unlike the major battles in Asia Minor. Garrisons and new settlements consolidated control, but conquest also involved coercion and violence.

In 327 BC the army moved into the northwestern Indian subcontinent. Victory over Porus at the Hydaspes in 326 BC did not ensure unlimited advance: at the Hyphasis, the soldiers refused to go farther. Sources connect their refusal with fatigue, campaign conditions and the prospect of further enemies; identifying all illnesses as viral without medical evidence is unjustified.

The return included movement along the Indus and the difficult crossing of Gedrosia. Alexander reorganised his empire in 324 BC and died at Babylon in 323 BC. There were potential dynastic heirs, including the unborn Alexander IV, but no undisputed adult successor. The commanders’ struggle, not simply the absence of an heir, brought the unified monarchy apart.

Related topics

• Ancient Greece

Literature and sources

• Arrian. Anabasis of Alexander.
• Plutarch. Alexander.