The Macedonians could be united by powerful leaders, but their nobility tended to be selfish and jealous of power. Since he named no heir, Alexander almost guaranteed that his empire would collapse as his generals turned on each other. Indeed, within a year of his death the empire plunged into civil war; it took until 280 BCE for the fighting to cease and three major kingdoms to be established, founded by the generals Antigonus, Ptolemy, and Seleucus.
The Antigonids ruled over Macedon and Greece. Despite controlling the Macedonian heartland and Greece itself, the Antigonids were the weakest of the Hellenistic monarchies. Both areas were depopulated by the wars; many thousands of soldiers and their families emigrated to the new military colonies established by Alexander, weakening Greece and, of course, its tax base. Over time, the Antigonids had to fight to hold on to power in Greece alone and they ultimately saw many of the Greek poleis achieve independence from their rule.
The Ptolemies ruled over Egypt. The Ptolemies were very powerful and, perhaps more importantly, they had the benefit of ruling over a coherent, unified state that had ancient traditions of kingship. Once they cemented their control, the Ptolemies were able to simply act as pharaohs, despite remaining ethnically and linguistically Macedonian Greek. In their state, the top levels of rule and administration were Greek, but the bulk of the royal bureaucracy was Egyptian. There were long-term patterns of settlement and integration, but right up to the end the dynasty itself was fiercely proud of its Greek heritage, with Greek soldier colonies providing the backbone of the Ptolemaic military. Ptolemy had been a close friend and trusted general of Alexander, and he took Alexander’s body to Egypt and buried it in a magnificent tomb in Alexandria, thereby asserting a direct connection between his regime and Alexander himself. In the end, the Ptolemies were the longest-lasting of the Hellenistic dynasties.
The Seleucids ruled over Mesopotamia and Persia. Despite the vast wealth of the Seleucid kingdom, it was the most difficult one to govern effectively. There was a relative scarcity of Greeks vis-à-vis the native populations, and it was thus also the most diverse. It proved impossible in the long term for the Seleucid kings to hold on to the entire expanse of territories originally conquered by Alexander. Seleucus himself gave his Indian territory back to Indian princes in 310 BCE in return for some elephants, and in 250 BCE a Persian clan, the Parthians, destroyed Seleucid control in the old Persian heartland, in the process founding a new Persian empire. Nevertheless, the Seleucid kingdom held on until its remnants were defeated by Pompey the Great of Rome (ally and then rival of Julius Caesar) in 69 BCE.
Each of the successor kingdoms was ruled by Greeks and Macedonians but the bureaucracies were staffed in large part by “natives” of the area. A complex relationship emerged between the cultures and languages of the kingdoms. Greek remained the language of state and the language of the elites, the Persian trade language of Aramaic was still used across most of the lands, and then a host of local tongues existed as the vernacular. The kings often did not speak a word of the local languages; as an example, Cleopatra VII (the famous Cleopatra who had affairs with both Julius Caesar and the Roman general Mark Antony) was the first Ptolemaic monarch to speak Egyptian.
All of the Hellenistic monarchs tried to rule in the style of Alexander, rewarding their inner circles with riches, founding new cities, and expanding trade routes to foreign lands. They also warred with one another, however, with the Ptolemies and the Seleucids emerging as particularly bitter rivals, frequently fighting over the territories that divided their empires. The kingdoms fielded large armies, many of which consisted of the descendants of Greek settlers who agreed to serve in the armies in return for permanent land-holdings in special military towns.
The Ptolemaic kingdom is particularly noteworthy: starting with Ptolemy himself, the existing Egyptian bureaucracy was expanded and its middle and upper ranks staffed entirely by Greeks (and Macedonians), who developed obsessively detailed records on every sheaf of wheat owed to the royal treasury. So much papyrus was used in keeping records that old copies had to be dumped unceremoniously in holes in the desert to make room for new ones - quite a lot of information about the Ptolemaic economy survived in these dumps to be discovered by archaeologists a few thousand years later. Likewise, the abundance of the Nile was carefully managed to produce the greatest yields in history, so large that even after numerous taxes were taken, Egyptian wheat was still the cheapest available everywhere from Spain to Mesopotamia (the same held true with papyrus, a royal monopoly used everywhere in the Hellenistic world). Under the Ptolemies, Egypt was in many ways at its most prosperous in history, outstripping even the incredible bounty of the Old, Middle, and New Kingdoms centuries earlier