In spring 334 BCE, Alexander III led the Macedonian-led force across the Hellespont into Achaemenid-held Asia, opening the campaign that would dismantle Persian rule in the western satrapies.
In 334 BCE Alexander besieged and captured Miletus, an important Ionian port; its fall strengthened Macedonian control of the Aegean-facing coast and reduced Persian naval leverage in the region.
Later in 334 BCE, Alexander took Halicarnassus after a major siege, breaking a key Persian stronghold in Caria and helping consolidate Macedonian authority in southwestern Anatolia.
Alexander won his first major victory in Asia at the Granicus River in May 334 BCE, helping secure a foothold in Anatolia and accelerating defections from Persian control.
At Issus on 333-11-05, Alexander defeated Darius III, forcing the Persian king to flee and leaving much of the empire’s western defenses vulnerable to continued Macedonian advance.
From January to July 332 BCE, Alexander captured the island city of Tyre after a prolonged siege, a strategic turning point that undermined Achaemenid influence along the Levantine coast.
In October 332 BCE Alexander took Gaza after a hard-fought siege, securing access to Egypt and further isolating remaining Persian positions in the eastern Mediterranean.
In 331 BCE, while Alexander campaigned in Asia, his regent Antipater defeated the Spartan king Agis III near Megalopolis, suppressing a major Greek uprising that had drawn on Persian support.
Alexander founded Alexandria in April 331 BCE, establishing a new coastal city intended as a durable Macedonian-Greek center in Egypt and a strategic Mediterranean hub.
On 331-10-01, Alexander’s victory at Gaugamela shattered Darius III’s main field army and effectively decided the outcome of the war, marking the decisive military collapse of Achaemenid power.
In October 331 BCE, soon after Gaugamela, Babylon surrendered and Alexander entered the city, gaining control of a major administrative and symbolic center of the Achaemenid realm.
On 330-01-20, Alexander forced the Persian Gate, overcoming a determined defense that briefly slowed his advance into Persis and cleared the way to the ceremonial heartland of Achaemenid rule.
By late January 330 BCE, Alexander entered Persepolis, taking control of the Achaemenid ceremonial capital and its vast treasury—an economic windfall that strengthened his ability to sustain further campaigning.
In 330 BCE, the palace complex at Persepolis was burned during Alexander’s occupation—an episode with contested motives in ancient sources, but widely treated as a symbolic rupture with Achaemenid imperial legitimacy.
In 330 BCE, after fleeing again following Gaugamela, Darius III was deposed and killed by the satrap Bessus as Alexander advanced; Darius’s death removed the last universally recognized Achaemenid monarch.
Fall of the Achaemenid Empire and Alexander's conquest (334–330 BCE)
