Alexander’s Empire: Conquest, Administration, and Breakup

Alexander’s empire grew from the Macedonian kingdom and the authority his father, Philip II, had established over much of Greece. Between 336 and 323 BCE, Alexander secured Macedon’s frontiers, defeated the Achaemenid Persian Empire, and campaigned as far east as the Indus region. His territories stretched from the Balkans and Egypt across western and central Asia, but they did not form a uniform or settled state. Alexander adapted existing forms of rule, appointed governors and local leaders, and relied on armies, garrisons, revenues, and new settlements to hold distant regions. His death in Babylon in 323 BCE left no adult successor, and rival commanders gradually replaced the empire with separate kingdoms. In Macedon, Antipatrid and then Antigonid rulers maintained a kingdom that eventually came under Roman rule.

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From Macedonian power to an Asian empire

Alexander became king after Philip II was assassinated in 336 BCE. Before beginning the invasion of Asia, he moved against revolts in Greece and the northern Balkans. He reasserted Macedonian authority in Thessaly and campaigned in Thrace and Illyria. When Thebes rebelled, he destroyed the city and divided its territory among neighbouring Boeotian communities. These campaigns secured the routes and political base behind the expedition his father had prepared against Persia.

In 334 BCE, Alexander crossed the Hellespont into Asia Minor. His advance combined military victories with the surrender or capture of regional capitals and coastal cities. Control of the Aegean coast mattered because Persian naval forces could otherwise threaten his communications and supply lines. Alexander’s forces moved through Asia Minor and then south into Syria and Phoenicia. The lengthy siege of Tyre in 332 BCE removed a major Persian naval base. After taking Gaza, Alexander entered Egypt, where he was recognized as ruler and made arrangements for military occupation and the collection of revenue.

From Egypt, Alexander returned to the campaign against Darius III. His victory at Gaugamela in 331 BCE opened the way to Babylon and the Persian capitals of Susa and Persepolis. Darius was killed while fleeing east in 330 BCE. This ended effective Achaemenid royal resistance, but it did not make every eastern province secure. Alexander continued campaigning in Bactria and Sogdiana, confronting local opposition and the forces of Bessus and Spitamenes. In 326 BCE he fought King Porus at the Hydaspes in the Punjab. His troops refused to advance farther east at the Hyphasis River, so Alexander turned back.

The sequence of campaigns helped Alexander avoid fighting for the whole empire at once. He first consolidated his position in Greece and the Balkans, then took coastal and western territories before moving into the Persian heartland. The eastern campaigns followed the defeat of Darius, as Alexander sought to make his authority effective beyond the former imperial capitals. This expansion depended on Macedonian forces, Greek allies and mercenaries, and troops and resources drawn from the territories he entered. Victory could bring surrender, but the continuing resistance in central Asia showed that defeating an imperial army was not the same as securing every province.

Governors, local rulers, and royal control

Alexander did not replace the Achaemenid administrative system throughout his conquests. He used its provincial divisions, known as satrapies, and appointed or retained satraps, meaning governors responsible for governing a province. Some former officials submitted and remained in office; elsewhere Alexander installed new governors or divided responsibilities among different authorities. The arrangements varied by region and could change when a governor appeared disloyal or too powerful.

In some provinces, Alexander separated the satrap’s civil authority from the collection of taxes and tribute. This gave the king a means of monitoring provincial revenues and limited the chance that a governor could use both local administration and financial resources to build an independent power base. The system still depended on the king’s appointments and the presence of reliable officers. Alexander also relied on local rulers where they could help maintain order. In Caria, Ada retained a position of authority after accepting his rule; in the Punjab, Porus continued to govern his kingdom as a subordinate ruler.

Policy toward Greek cities also differed from place to place. In parts of Asia Minor, Alexander allowed some cities to retain self-government and political arrangements, while requiring allegiance and support for his campaign. In Egypt, he retained local religious practices and restored temples, while placing the territory under Macedonian oversight. These examples show that the empire was held together through a mixture of royal officials, local rulers, city governments, and military force, not through a single uniform system.

Garrisons, settlements, and the resources of conquest

Military occupation supported provincial government. Garrisons could secure strategic routes and important centres, while the army’s continued presence discouraged resistance. Alexander also founded or planned new settlements, many bearing the name Alexandria. Their locations could serve defensive or administrative purposes and connect with routes of movement and trade. Some settlements began as military posts; in time, others attracted Greek settlers and local inhabitants and developed into towns.

These forces and officials depended on supplies and money. Alexander drew on revenues from provinces, tribute, and the treasuries captured at Persian centres such as Susa. Macedon also had an established source of precious metals: Philip II’s conquests brought gold and silver mines, including those around Mount Pangaeum, under Macedonian control. The resulting wealth helped support the kingdom’s military power. Under Alexander, captured resources and provincial income could fund the army and the occupation of newly conquered territory.

Coinage helped turn captured bullion into payments for soldiers and other expenses. Standard Alexander-type silver issues showed Herakles in a lion skin on one side and Zeus seated with an eagle and sceptre on the other. The images made royal silver recognisable across different mints, while older currencies and local payments continued alongside it. Successor rulers also struck Alexander’s types after his death, extending the currency’s use beyond the empire’s unity.

The succession crisis after 323 BCE

Alexander died in Babylon in 323 BCE. His half-brother, Philip III Arrhidaeus, could be made king, but Alexander’s wife Roxana was pregnant, and the child’s sex was not yet known. The infantry and cavalry disagreed over the settlement. A compromise recognized Philip III and, after Roxana gave birth to a son, Alexander IV as joint kings. They were kings in name, while commanders and regents exercised power on their behalf.

Perdiccas, who had been a leading officer at court, became regent in the first settlement. At the Partition of Babylon, Alexander’s commanders assigned satrapies and military or political responsibilities among themselves. Antipater retained control of Macedon and Greece; Ptolemy received Egypt; and other commanders took positions in Thrace and across Asia. These appointments did not immediately declare the empire dissolved. The kings remained its formal focus, but each governor had a regional power base, and the commanders had their own troops and ambitions.

Conflict soon broke out. Antipater, Ptolemy, Antigonus, and other commanders opposed Perdiccas’s attempt to strengthen his control. Perdiccas’s invasion of Egypt failed, and his own officers killed him in 321 BCE. A new settlement at Triparadisus confirmed Antipater as regent and rearranged appointments. Yet agreements could not resolve the deeper problem: no uncontested successor could command the army and bind the distant provinces together. The wars among Alexander’s successors, called the Diadochi, continued for decades.

Antipatrid rule and the end of the royal family

Antipater died in 319 BCE and chose Polyperchon, rather than his son Cassander, as regent. Cassander challenged the appointment and joined forces with rivals of Polyperchon. Their struggle brought warfare to Macedon and Greece and involved the royal family directly. Philip III and his wife Eurydice were killed in 317 BCE, and Cassander gained control of Macedon. Alexander IV and Roxana remained alive for a time under his authority, but they too were killed by 310 BCE. With Alexander’s direct heirs removed, the commanders had less reason to preserve the appearance that they governed only on behalf of the Argead royal house.

The Antipatrid period was therefore not a stable transfer of hereditary rule. Cassander’s control emerged from military and political conflict, and the subsequent struggle over Macedon continued after his death in 297 BCE. His sons disputed power, creating an opening for Demetrius, son of Antigonus Monophthalmus, who became king of Macedon in 294 BCE. Demetrius later lost the kingdom, and control remained contested until Antigonus II Gonatas established Antigonid rule in the late 270s BCE.

Antigonid Macedon and Roman intervention

Antigonus Monophthalmus had sought to dominate Alexander’s former empire. His power and that of his son Demetrius alarmed rival commanders, who formed a coalition against him. At the Battle of Ipsus in 301 BCE, Antigonus was killed. The defeat ended the most serious remaining attempt to reunite the empire under one ruler. The balance among the successor powers continued to shift, but separate kingdoms became the lasting political reality.

The Antigonids eventually secured Macedon, while the Ptolemaic kingdom ruled Egypt and the Seleucid kingdom controlled extensive territories in Asia. These states inherited parts of Alexander’s administrative and military systems, but they were independent monarchies, not provinces of a restored empire. Macedonian rulers still intervened in Greece and relied on military power to protect their position. In the second century BCE, Roman victories ended Antigonid rule and brought Macedon under Roman control. Alexander’s empire had thus given way not to one successor state, but to competing kingdoms whose political boundaries and fortunes changed over time.

For the wider setting, see The Macedonian Kingdom: From the Argead Dynasty to Roman Rule.