Why did the Empire of Alexander the Great fragment after his death
Alexander the Great (356-323 BC) was one of the greatest generals of all time, and his conquests and brief reign changed the history of the world. Once the great Macedonian had dreamt of a universal Empire that encompassed the known world. However, the realm that he created did was short lived and quickly fragmented.
Within a few years of his death, Macedonian generals had divided his territories into various Hellenistic states. Several factors caused the sudden collapse of the Empire that Alexander built. These include the early and the somewhat unexpected death of the great king, absence of a capable successor, rebellious generals, and the size of the territories Alexander had invaded. Instead of creating a vast empire, Alexander's dream collapsed into numerous warring kingdoms.
Alexander the Great became king of Macedonia after the death of his father, Phillip II. He had inherited a powerful kingdom and an overflowing treasury, but above all, he took control of the Macedonian army which often regarded by scholars as one best fighting forces in the history of warfare. After putting down a rebellion in Greece and securing Macedonia’s frontiers, he launched an invasion of the Achaemenid Persian Empire, which spanned much of Western Asia. He claimed that he was waging a war of revenge in retaliation for the two previous Persian invasions of Greece.
Alexander defeated the Persians at the River Granicus (332 BC), and he swiftly conquered all of Asia Minor (Turkey). The Great Persona King Darius II assembled a large army and confronted Alexander at the River Issus (332BC). The Macedonian was once again victorious, and he went on to capture Egypt. The Achaemenid monarch offered to cede to the son of Phillip II, the western portion of his Empire if he stopped his aggression. Alexander rejected this and invaded the heartland of the Persian state.
At the battle of Gaugamela, he wrecked Darius's army and proceded to annex all of Persia. The Macedonian monarch pursued Darius II into Central Asia but failed to capture him before he was assassinated by one of his generals. Alexander’s conquests provided a great administrative challenge, and he adopted the Persian system of satrapies or semi-autonomous territorial units, which were ruled by his Macedonian lieutenant. He also chose a conciliatory policy towards the Persians, as evidenced by his treatment of the family of Darius.
Alexander alienated many of his generals by his actions. In particular, they disliked the fact that he began to assume the prerogatives and manners of an Oriental monarch and was introducing Persians into the army. The conqueror was not content with his vast domains and wanted to conquer the known world. He invaded north-west India and successfully annexed several kingdoms before his troops mutinied and forced him to turn back. The retreat from India was a disaster, and many died crossing the Gederosian Desert. Alexander returned to Babylon, but he soon developed a fever and fell gravely ill and died at the age of 32 in 323 BC.
Civil War and Disintegration
The generals in the army soon usurped control of the Empire. They at first agreed to cooperate and to hold the Empire together in the name of Alexander’s brother who was crowned King Phillip III. Alexander’s infant son from his wife Roxana was made co-ruler with Phillip III after his birth. The royal family was sent to Macedonia to the royal capital at Pella. The great general Perdiccas was the Regent, and he was technically the supreme commander of the army. Immediately there were problems because Macedonian generals began to pursue their interests and formed private armies. There were several conspiracies involving members of the dead king’s extended family.
Moreover, many of the generals became suspicious of Perdiccas who appeared to be seeking to elevate himself to the emperor of Alexander's kingdom. This led to the first War of the Diadochi or Successors of Alexander. By 321 AD, Ptolemy the satrap of Egypt was acting like an independent ruler. Ptolemy then seized Alexander's body which was perceived as an attempt to anoint himself as Alexander’s heir. Perdiccas attempted to invade Egypt, but he bungled the crossing of the Nile, and his generals later assassinated him. Antigonus defeated Eumenes, who had regarded himself as the successor of Perdiccas and he became the most powerful ruler in the lands conquered by Alexander.
However, much of the Empire was outside of his control, and Antigonus sought to reunite all the lands that had been conquered by Alexander. There were three more civil wars, between the successors of Alexander that ravaged an area from Greece to Central Asia. At this time, Seleucus was forced to concede, the satrapies in India to the rising regional superpower the Mauryan kingdom. The fourth Diadochi war was decided at the Battle of Ipsus (301 AD). Here Antigonus was defeat by a coalition led by Seleucus. 
The aftermath of the battle was the final partition of the Macedonian Empire. There were no further attempts to reunify the lands conquered by Alexander the Great. After some additional conflicts, by 280 BC, Alexander’s conquests were finally divided between the Seleucids in Asia, the Ptolemies in Egypt, and the Antigonids in Macedonia. These kingdoms proved durable, and the successor states endured for roughly 200 years.
The early death of Alexander
Alexander died after a short illness in the former palace of the Babylonian kings. The sudden demise of a man who seemed a force of nature and widely seen as a demi-god shocked even his enemies. Many, at the time, believed that he was poisoned possibly by one of his generals. There had been conspiracies before aimed at Alexander such as the ‘Conspiracy of the Pages.’ 
However, most scholars and medical experts argue that he died of either the complications of a wound, he had received in India or from typhoid fever. The sudden death of the greatest monarch of his time left a power vacuum in his state. There was no central authority, and this was very destabilizing. Alexander had ruled as an autocrat, and anyone who opposed him could technically be executed. He was the absolute ruler of his territories and had controlled both his army and satraps very tightly despite his constant campaigning.
Alexander's sudden death allowed ambitious individuals to pursue their interests at the expense of the greater Empire. The death of Alexander meant that the army did not have a single leader. Rival generals ignored their superiors and followed their interests, and this was to the detriment of the unity of the Empire. Immediately after the death of Alexander, at the Compromise of Babylon, which prevented a civil war, the generals divided the conquests into their respective spheres of influence.
Lack of a successor
While Alexander left a will, ordering further conquest and ambitious construction projects, he failed to the state should succeed him and wear the crown. The death of Alexander meant that his throne and all his realms should have passed to his heir. This was far from straightforward. He had an infant son, but he was declared to be illegitimate. His lawful wife was pregnant, but it was not certain if the baby would live or if it would be a male.
Under Macedonian succession law, only males could be crowned. However, his half-brother was alive and was in his twenties. Under the Compromise of Babylon, he was recognized as Philip III Arrhidaeus. He had accompanied Alexander on all his campaigns and was present at his death. Phillip appears to have had some intellectual disability and was not capable of ruling. He soon became the pawn of the generals and especially Perdiccas. When Roxanne, Alexander’s wife gave birth to a boy, he was named as Alexander IV of Macedonia. Perdiccas sent them to Pella where they were held as virtual prisoners. The real power lay now with the generals, and the heirs of Alexander were only puppets. Phillip III and Alexander IV were both assassinated and with them ended the line of Alexander.
The lack of an able and mature successor meant that the Empire was almost bound to fall into a state of civil war. When there was no clear succession plan in kingdoms in the ancient world instability inevitably followed the death of the monarch. Without a strong king at the head of the army and the state, power fell into the hands of the strongest, and these were the generals. They had become very ambitious, even during the lifetime of Alexander. Many of them when they served as satrapies often acted like independent monarchs. The lack of a ruler meant that power passed to the generals and they began a series of power struggles that caused the unified Empire of Alexander to fragment into a series of different successor states.
The Scale of the Empire
The early death of Alexander and the absence of any heir that could control the ambitions of the generals and others were crucial factors in the disintegration of the Empire. However, there are those who argue that even if there had been an orderly succession and the army had remained united that it would have fragmented in due course. The sheer extent of Alexander’s realm is estimated to have been 2 million square miles (5 million kilometers). Communications at the time were very slow and, furthermore, the Macedonian Empire was very diverse and divided by religion, ethnicity, and language.
Alexander had the charisma and authority to impose his will on the regions. However, even he had to give a great deal of autonomy to his governors and was troubled by rebellious satraps . The vast Empire would have been very hard to keep together even had the great conqueror lived and had a capable successor. Once he died, there was no central authority to maintain unity. The scale of the territories was such that it was almost impossible to govern effectively. Instead, local military leaders often usurped entire provinces with impunity and became de-facto independent. This situation repeated itself with Ptolemy in Egypt, Seleucus in Babylon and Lysimachus in Thrace.
The sheer scale of the conquests of Alexander allowed generals to carve out often large states. Moreover, the regions required these local strongmen, who could deal with issues on the spot. Only they could maintain order and defend the frontiers because any central authority would have been too far away and distant. The need for these strong local rulers was another factor in the break-up of one of the largest Kingdoms in world history.
In an astonishingly brief period, Alexander conquered a huge Empire. However, it just as quickly collapsed it fragmented into a series of warring Empires and Kingdoms. Strictly speaking, the Empire of Alexander only lasted little more than a decade and could be said to have begun to break up after his burial. The cause of the collapse of the great realm can be attributed to several factors. The first was the early death of Alexander which left his kingdom in a state of disarray and more importantly meant that the army was no longer under central control. The generals became the de-facto rulers of the lands conquered by Alexander and fought many civil wars to secure a share of the spoils. Then there was no successor to the Macedonian monarch only an infant and a man who had some form of developmental deficit. The sheer scale of the territories conquered by Alexander also contributed to the fragmentation of the Empire.
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