The first struggle was over the regency; theoretically Alexander's feeble-minded brother, Philip, and also Alexander's posthumous son by Roxana had the real claim to the inheritance. Perdiccas had the regency (323-322), in effect if not in name, to which Antipater also had claim. Eumenes supported Perdiccas, while Antigonus, Ptolemy, and Craterus supported Antipater. In 321, battle was joined; the allies of Antipater won, although Craterus was killed. On the death (319) of Antipater the struggle was on again. There were shifting alliances, but in general the chief figure was Antigonus, who, with the help of his son, Demetrius Poliorcetes (Demetrius I of Macedon), attempted to rebuild Alexander's empire. He failed. Antigonus and Demetrius were finally defeated in the battle of Ipsus (301 B.C.). The Diadochi had been declaring themselves kings, Antigonus first and then the others.
The contest was carried on to the next generation, with Demetrius fighting successfully against Cassander, the son of Antipater, and it was pursued even further with the wars between the Seleucidae and the Ptolemies. Commonly, however, the period of the Diadochi is said to end with the victory of Seleucus I over Lysimachus at the battle of Corupedion in 281, fixing the boundaries of the Hellenistic world for the next century. This left the descendants of Ptolemy, Seleucus, and Antigonus as the chief claimants to power in the Hellenistic age, and the empire of Alexander was irrevocably split.
The Diadochi (plural of Latin Diadochus, from Greek Διάδοχοι, Diadokhoi, "successors") were the rival successors of Alexander the Great, and their Wars of the Diadochi followed Alexander's death. This was the beginning of the Hellenistic period of Greek history, the time when many people who were not Greek themselves adopted Greek philosophy and styles, Greek urban life, and aspects of the Greek religion. They are also referred to as Epigonoi (Greek: Ἐπίγονοι, "offspring"),
Upon Alexander's untimely death, there was almost immediately a dispute among his generals as to who his successor should be. Meleager and the infantry supported the candidacy of Alexander's half-brother, Arrhidaeus, while Perdiccas, the leading cavalry commander, supported waiting until the birth of Alexander's unborn child by Roxana. A compromise was arranged - Arrhidaeus (as Philip III) should become King, and should rule jointly with Roxana's child, assuming that it was a boy (as it was, becoming Alexander IV). Perdiccas himself would become Regent of the entire Empire, and Meleager his lieutenant. Soon, however, Perdiccas had Meleager and the other infantry leaders murdered, and assumed full control.
The other cavalry generals who had supported Perdiccas were rewarded in the partition of Babylon by becoming satraps of the various parts of the Empire. Ptolemy received Egypt; Laomedon received Syria and Phoenicia; Philotas took Cilicia; Peithon took Media; Antigonus received Phrygia, Lycia and Pamphylia; Asander received Caria; Menander received Lydia; Lysimachus received Thrace; Leonnatus received Hellespontine Phrygia; and Neoptolemus had Armenia. Macedon and the rest of Greece were to be under the joint rule of Antipater, who had governed them for Alexander, and Craterus, Alexander's most able lieutenant, while Alexander's old secretary, Eumenes of Cardia, was to receive Cappadocia and Paphlagonia.
In the east, Perdiccas largely left Alexander's arrangements intact - Taxiles and Porus ruled over their kingdoms in India; Alexander's father-in-law Oxyartes ruled Gandara; Sibyrtius ruled Arachosia and Gedrosia; Stasanor ruled Aria and Drangiana; Philip ruled Bactria and Sogdiana; Phrataphernes ruled Parthia and Hyrcania; Peucestas governed Persis; Tlepolemus had charge over Carmania; Atropates governed northern Media; Archon got Babylonia; and Arcesilas ruled northern Mesopotamia.
Ptolemy came to terms with Perdiccas's murderers, making Peithon and Arrhidaeus regents in his place, but soon these came to a new agreement with Antipater at the Treaty of Triparadisus. Antipater was made regent of the Empire, and the two kings were moved to Macedon. Antigonus remained in charge of Phrygia, Lycia, and Pamphylia, to which was added Lycaonia. Ptolemy retained Egypt, Lysimachus retained Thrace, while the three murderers of Perdiccas--Seleucus, Peithon, and Antigenes--were given the provinces of Babylonia, Media, and Susiana respectively. Arrhidaeus, the former Regent, received Hellespontine Phrygia. Antigonus was charged with the task of rooting out Perdiccas's former supporter, Eumenes. In effect, Antipater retained for himself control of Europe, while Antigonus, as leader of the largest army east of the Hellespont, held a similar position in Asia.
In the east, Eumenes was gradually driven back into the east by Antigonus's forces. After great battles at Paraitacene in 317 BC and at Gabiene in 316 BC, Eumenes was eventually betrayed and murdered by his own troops in 315 BC, leaving Antigonus in undisputed control of the Asian territories of the Empire.
At about the same time, Cassander had young King Alexander IV and his mother Roxane murdered, ending the Argead Dynasty which had ruled Macedon for several centuries. For the moment, all of the various generals continued to recognize the dead Alexander as King, since Cassander did not publicly announce the deaths, but it seemed clear that at some point, one or the other of them would claim the Kingship.
In 306, Antigonus attempted to invade Egypt, but storms prevented Demetrius's fleet from supplying him, and he was forced to return home. Now, with Cassander and Ptolemy both weakened, and Seleucus still occupied in the East, Antigonus and Demetrius turned their attention to Rhodes, which was besieged by Demetrius's forces in 305 BC (see siege of Rhodes). The island was reinforced by troops from Ptolemy, Lysimachus, and Cassander. Ultimately, the Rhodians reached a compromise with Demetrius - they would support Antigonus and Demetrius against all enemies, save their great ally Ptolemy. Ptolemy took the title of Soter ("Savior") for his role in preventing the fall of Rhodes, but the victory was ultimately Demetrius's, as it left him with a free hand to attack Cassander in Greece. Demetrius returned to Greece, defeated Cassander, and formed a new Hellenic League, with himself as General, to defend the Greek cities against all enemies (and particularly Cassander).
In the face of these catastrophes, Cassander sued for peace, but Antigonus rejected the claims, and Demetrius invaded Thessaly, where he and Cassander faced off against each other in inconclusive engagements. But now Cassander called in aid from his allies, and Anatolia was invaded by Lysimachus, forcing Demetrius to leave Thessaly and send his armies to Asia Minor to assist his father. With assistance from Cassander, Lysimachus overran much of western Anatolia, but was soon (301 BC) isolated by Antigonus and Demetrius near Ipsus. Here came the decisive intervention from Seleucus, who arrived in time to save Lysimachus from disaster and utterly crush Antigonus at the Battle of Ipsus. Antigonus was killed in the fight, and Demetrius fled back to Greece to attempt to preserve the remnants of his rule there. Lysimachus and Seleucus divided up Antigonus's Asian territories between them, with Lysimachus receiving western Asia Minor and Seleucus the rest, except Cilicia and Lycia, which went to Cassander's brother Pleistarchus.
Soon, Demetrius was forced from Macedon by a rebellion supported by the alliance of Lysimachus and Pyrrhus, who divided the Kingdom between them, and, leaving Greece to the control of his son, Antigonus Gonatas, Demetrius launched an invasion of the east in 287 BC. Although initially successful, Demetrius was ultimately captured by Seleucus (286 BC), drinking himself to death two years later.
Dynastic struggles also rent Egypt, where Ptolemy decided to make his younger son Ptolemy Philadelphus his heir rather than the elder, Ptolemy Ceraunus. Ceraunus fled to Seleucus. The eldest Ptolemy died peacefully in his bed in 282 BC, and Philadelphus succeeded him.
Soon Lysimachus made the fatal mistake of having his son Agathocles murdered at the say-so of his second wife, Arsinoe (282 BC). Agathocles's widow, Lysandra, fled to Seleucus, who now made war upon Lysimachus. Seleucus, after appointing his son Antiochus ruler of his Asian territories, defeated and killed Lysimachus at the battle of Corupedium in Lydia in 281 BC, but Seleucus did not live to enjoy his triumph for long - he was almost immediately murdered by Ptolemy Ceraunus, for reasons that remain unclear.
Ptolemy Ceraunus was also not to enjoy the rule of Macedon for very long. The death of Lysimachus had left the Danube border of the Macedonian kingdom open to barbarian invasions, and soon tribes of Gauls were rampaging through Macedon and Greece, and invading Asia Minor. Ptolemy Ceraunus was killed by the invaders, and after several years of chaos, none other than Antigonus Gonatas emerged as ruler of Macedon. In Asia, Seleucus's son, Antiochus I, also managed to defeat the Celtic invaders, who settled down in central Anatolia in the part of eastern Phrygia that would henceforward be known as Galatia after them.
Now, at long last, almost fifty years after Alexander's death, some sort of order was restored. Ptolemy ruled over Egypt, southern Syria (known as Coele-Syria), and various territories on the southern coast of Asia Minor. Antiochus ruled the vast Asian territories of the Empire, while Macedon and Greece (with the exception of the Aetolian League), fell to Antigonus.
This division was to last for a century, before the Antigonid Kingdom finally fell to Rome, and the Seleucids were harried from Persia by the Parthians. A rump Seleucid kingdom limped on in Syria until finally put to rest by Pompey in 64 BC. The Ptolemies lasted longer in Alexandria: Egypt finally fell to Rome in 30 BC.