The reason for Alexander’s untimely end – he was one month short of his 33rd birthday – is unknown. The three leading theories are poisoning, a relapse of malaria or some sort of illness brought on by feasting on May 29. Alexander took ill right after that feast, and never left his bed again afterwards. He died on either the 10th or 11th or June.
Alexander’s death was also the death knell of his empire. Over the next five decades, the empire would fall into civil war, and by 270 BCE it would have devolved into three successor states, the Antigonid Empire in Greece; the Ptolemaic Kingdom in Egypt, Palestine and Cyrenaica; and the Seleucid Empire in Mesopotamia and Persia. The former two would be wholly absorbed by Roman expansion over the next three centuries, along with the western half of the territory of the Seleucid Empire.