Amongst his generals who took parts of it and formed what we call the Hellenistic Kingdoms.
On his deathbed, Alexander was prompted to give the name of his successor - this he did not do or was unable to do. Of course there are speculations on words that he may have muttered - such as kratistos meaning 'the strongest' but it also could have been the name of one of his comrades Krateros - but this will probably never be proven. As Alexander had no legitimate heir, a regent was appointed to look after his empire, which was thus divided into different lands between several of his comrades. Therefore, the empire was no more and separate smaller empires and kingdoms were formed. For further information, look at the Seleucids, the Ptolomies and the Antigonids.
Amongst his generals who took parts of it and formed what we call the Hellenistic Kingdoms.
His generals split up the empire and formed their own kingdoms (today we call them the Hellenistic Kingdoms).
Alexander the Great
The Seleucid Empire formed when The Macedonian Empire ( Empire of the Macedonians / empire of Macedon collapsed . After Alexander the Great Died there was no evident heir to the throne . His last words were na naisilnite ( на најсилните ) - to the strongest . this was in terms of the heir to the empire . His empire fell into chaos as his generals fought over his empire . eventually , the Turks formed The Seleucid Empire and took the empires land leaving them with their european territory only . With the exception of northern Thrace . it is debated weather it was taken by Bulgarians , or Thracian rebels .
He didn't build the empire, he simply took it over from the Persians. After his early death, his generals fought each other and split the empire amongt themselves and formed their own kingdoms.
Great spoils for the Macedonian conquerors who, after Alexander's death, divided the empire amongst themselves and formed kingdoms of their own in Egypt, Syria-Mesopotamia, Asia Minor and mainland Greece.
There was no Greek empire - the Greek world was a lot of city-states which sometimes formed self-defence leagues. The Macedonian empire under Alexander the Great included Egypt and the lower Nile River.
The Akkadian empire was formed by Sargon because he divided the empire into 70 smaller pieces
There was no Greek empire to battle. Greece was hundreds of independent city-states, some of which from time to time formed defensive leagues. Alexander's father king Philip II of Macedonia (with son Alexander as one of his commanders) progressively overcame these cities and leagues in mainland Greece, and was appointed Hegemon (leader), and planned a campaign in Asia against the Persian Empire. On his death Alexander inherited the kingship of Macedonia and Hegemon of Greece, and continued on with his father's plan to defeat the Persian Empire, and establish his own.
His generals after his death divided the empire up between them.