It is one thing to conquer and empire but another thing to
Alexander's empire stopped expanding because when, after a lot
of hardships, his army reached the western edges of India, the men
refused to continue eastwards. They were tired of conquest and
wanted to get home.
They returned to Persia (after a terrible forced march through
the desert, where many died) which was intended to be the centre of
his Empire. On the way there, Alexander's lover Hephastion died,
possibly poisoned, possibly from poor medical care after a bout of
The loss seems to have driven Alexander partly insane - at one
point he seems to have tried to starve himself to death. He
recovered, and devised an immense state funeral for Hephastion, but
was never the same again.
Although he was still young he had also received terrible
injuries during the various battles he fought on his journey
eastwards - including one where an arrow pierced his lung,
shattering the rib and permanently damaging his breathing. He had
recovered and continued to lead his army from the front, but it was
taking its toll too.
When Alexander reached Babylon he caught a fever, possibly due
to bad water, refused treatment, stayed up late drinking with his
men (a Macedonian custom) and developed an infection from which he
soon died. Overwork, grief and much damage to his body probably
played its part.
He had no child and no obvious successor. His lesser wife (the
daughter of of Sogdian king) was certainly pregnant, and gave birth
to his son some months later. His chief wife (the daughter of the
last Persian emperor Darius) may have been pregnant, too, but she
was quickly murdered. His half-brother, Philip, was thought to be
an idiot: he was there with the army but never considered as a
serious successor. If Hephastion had survived, he (as
second-in-command) would probably have had a good chance of taking
over, but he was dead.
Without the dynamic, charismatic leader, the Empire he had only
just put together collapsed. Each of his generals grabbed what he
could, and they all fought each other. One of them kidnapped
Alexander's surviving wife and his son, and later had them
murdered. The Hellenistic empire became a number of different,
often warring, empires, each of them ruled by a Greek-speaking
dynasty descended from one or other Macedonian war leader.
The most successful was Ptolomy, who grabbed Egypt - and kept
it. His line lasted until the rise of the Roman Empire. Cleopatra
was a descendant of his.