Alexander
III of Macedon, student of Aristotle, succeeded the throne of Macedon
in 336 BCE, at age 20. News of his fathers assassination, rumoured to be
ordered by Persian king Darius III, inspired many of Macedons newly
vassalised Greek states to revolt, prompting Alexander to reassert
Macedonian authority over Greece (excluding Sparta), Thrace and Illyria.
Alexander was then ready to launch his fathers long-planned Persian
campaign, hoping to realize the goal of conquering the Achaemenid
Persian empire, stretching from India to Anatolia and Egypt. In 334
Alexander crossed the Hellespont into Anatolia with his entire army
where he beat the Anatolian provincial garrisons at the battle of the
Granicus, and began appointing his own governors to those provinces. In
333 king Darius personally led his troops to face Alexander in Eastern
Anatolia in the battle of Issus, where the heavily outnumbered Greeks
used the river bank to counter the Persian numerical superiority and
routed their foes. Never before had a Persian army led by their king
lost a battle.
Following this victory, Alexander invaded and gradually
subjugated the Persian Levant and Egypt.
By 331 Alexander had crossed the Euphrates, beginning the long march to
the Persian heartlands. Darius raised a massive army, equipped with war
elephants, to face the Macedonians at the battle of Gaugamela, modern
day Kurdistan. Chaos gripped the Persian army when it was wrongly
assumed Darius was killed, and a rout followed. Darius then reached out
to Alexander and offered him the title of co-emperor, official rulership
of all lands east of the Euphrates (Anatolia, Egypt, and the Levant),
the hand of one of his daughters in marriage, and over 1000 tons of
silver.