The Fourth Diadoch War (307-301) was the final stage of the struggle between Antigonus and his fellow successors (Diadochi) for control of the inheritance of Alexander the Great. By the end of 308 BC Cassander had eliminated the main threats to his position in Greece and Macedonia. Polyperchon had been bought off by an appointment as general of the Peloponnese. An Egyptian expedition of 308 had ended in failure. That expedition had been launched during a rare period of alliance between Ptolemy and Antigonus. When it failed, Antigonus needed to find a new way to disrupt Cassander’s efforts to consolidate his position in Greece.
Antigonus decided to take advantage of his public commitment to the liberty of the Greek cities. For ten years Athens had been ruled by a dictator who had been installed by Cassander. In 307 BC Antigonus sent his son Demetrius to Athens to depose Cassander’s regime, and restore the democracy. Demetrius was welcomed in Athens as a divine liberator, and settled down for a period of dedicated debauchery in the city.
This ended in 306 when open war broke out between Antigonus and Ptolemy. Demetrius was sent to conquer Cyprus. He began with a major siege of Salamis, failing to take the city by siege, but winning the battle of Salamis, a naval battle close to the city. Cyprus fell, and was to be an important base for Demetrius even after the fall of his father in 301.
Fourth Diadoch War
In the aftermath of the triumph on Cyprus, Antigonus was acclaimed as king (basileus). Antigonus was claiming Alexander’s legacy, and by right of conquest, or at least of military achievement. He was not claiming to be king of any particular area – when his grandson Antigonus Gonatas became king of Macedonia it would be as Antigonus II, despite Antigonus I never actually having control of Macedonia. Demetrius was also given the same title at this stage.
Once Antigonus had taken this step, his rivals soon followed. Ptolemy waited until he had seen off an attempted invasion by Antigonus that followed the victory on Cyprus, although the title only made sense to his Greek and Macedonian subjects. Seleucus, Cassander and Lysimachus each took the same step over the next year or so, although with differing levels of enthusiasm.
From Cyprus Antigonus turned his attention to Rhodes. Rhodes was one of the few Greek states to remain independent throughout this period, and was a powerful naval force. In 305 BC Demetrius was dispatched to Rhodes with orders to capture the city. The defences of Rhodes were formidable, and despite his best efforts Demetrius was unable to take the city. Ptolemy was able to keep the city supplied by sea, which suggests that his fleet was not as badly damaged at Salamis as is sometimes supposed. While Demetrius was occupied on Rhodes, Cassander was recovering his position in Greece and was now beginning to threaten Athens. In 304 Antigonus was forced to negotiate a compromise peace with Rhodes. The Rhodians agreed to support Antigonus as allies against anyone but Ptolemy. This freed Demetrius to return to Greece.
Once in Greece he was soon able to restore the situation. Cassander was still unpopular and Demetrius had yet to loose the goodwill he had generated in 307. By 302 Cassander had been pushed out of much of central Greece. Demetrius was able to form a new league of Greek cities, based at Corinth. This league was to be used as a weapon against Cassander. Demetrius was inevitably elected as general of the league’s army, and launched an attack on Cassander’s position that forced him to sue for peace.
Antigonus refused the offer of peace. He was now confident that he was on the brink of a total victory. Demetrius was to advance on Macedonia from the south, while he attacked from the east. Cassander would be crushed between the two armies.
This grand plan was never carried out. After the rejection of his peace offer, Cassander turned to Ptolemy, Seleucus and Lysimachus and was able to form a firm alliance against Antigonus. Lysimachus would lead his and Cassander’s armies east into Asia Minor. Seleucus made peace with Chandragupta in return for 500 war elephants. He would bring this army west, join with Ptolemy and the combined allied armies would overwhelm Antigonus, and hopefully Demetrius.
The plan worked almost perfectly. Faced with an invasion of Asia Minor, Antigonus summoned Demetrius from Greece. Lysimachus was able to delay the battle until Seleucus arrived. The only disappointment was that Ptolemy did not appear, instead preferring to conquer Coele-Syria instead. At the battle of Ipsus (301 BC) in Phrygia, Antigonus was defeated. He was killed in the battle, his army was crushed and Demetrius only just managed to escape.
The death of Antigonus removed the last figure whose consistent aim was to reunite Alexander’s empire. The victors of Ipsus were happy to establish their own limited kingdoms, although all but Ptolemy would have happily taken a change of greater glory if it came that way. Demetrius may have aimed at reclaiming all of his father’s lands, but his later adventures lacked any unity of purpose. The first half of the struggle between the successors had been between unifiers and separatists. The second half would be a battle to define the shape of the successor states.