Diadochi ("successors"): name of the first generation of military and political leaders after the death of the Macedonian king and conqueror Alexander the Great in 323 BCE. To settle the question whether his empire should disintegrate or survive as a unity, and, if so, under whose rule, they fought several full-scale wars. The result, reached by 300, BCE, was a division into three large parts, which more or less coincided with Alexander's possessions in Europe, Asia, and Egypt.
During the next quarter of a century, it was decided whether these states could endure. As it turned out, there were no great territorial changes, although there were dynastic changes. After 280, the period of state-forming came to an end with three great states: Antigonid Macedonia, Ptolemaic Egypt, and the Seleucid kingdom in Asia.
The significance of the Battle of Ipsus, in which Antigonus Monophthalmus and Demetrius Poliorcetes were defeated, is that from now on, the unification of Alexander's empire was forever impossible. The victors immediately divided the Asian territories of Antigonus: Lysimachus took large parts of what is now Turkey, although the southern parts (Lycia and Cilicia) were given to a brother of Cassander, Pleistarchus. Seleucus received Syria, Phoenicia, and Palestine, but discovered that large parts were in the meantime occupied by Ptolemy. They would be a major bone of contention between the Seleucids and Ptolemies in the third century. Finally, northern Cappadocia was awarded to a man named Ariarathes, and became a satellite of the Seleucid Empire.
By now, three large states were in the making: Ptolemy's Egypt, with an annex in Syria; Seleucus' Asia; and Lysimachus' Europe, which now included a part of Asia Minor. However, there was one disturbing element, Demetrius. He had escaped from Ipsus and still controlled large parts of the Peloponnese. But his popularity had diminished, because he had conscripted many men from the member states of the Greek League (above). On the other hand, he still commanded a large navy and was master of the Nesiotic League (above) and Cyprus. He was some sort of pirate king.
Cassander and Lysimachus had reason to fear the presence of the man in the region, and Ptolemy's Phoenicia lay dangerously exposed to his attacks. The three men concluded a treaty, which was confirmed by marriage (300): Ptolemy's daughter Arsinoe II was married to Lysimachus, and Lysandra was given to Lysimachus' son Agathocles. Another reason for this alliance may have been Ptolemy's fear that Seleucus would try to drive him out of Syria, Phoenicia, and Palestine. The new king of Asia was already building new cities (like Seleucia and Antioch).
Seleucus had nothing to fear from Demetrius, but understood that Ptolemy was preparing a war. He now allied himself to Demetrius and married his daughter Stratonice (299). Demetrius was now sufficiently covered, and expelled Cassander's brother from Lycia and Cilicia (298). At the same time, Seleucus raided Samaria in Palestine. Cassander was dying and could not intervene, and Ptolemy was so impressed by Demetrius and Seleucus, that he accepted a treaty.
Meanwhile, the Greeks had forgotten their alliance with Demetrius. For example, Athens had concluded a peace treaty with Cassander. This offered Demetrius a pretext to intervene in Greece, and in 296 he started to besiege Athens, which surrendered in 295. This time, the conqueror had lost his patience: there was no 'freedom and autonomy' for the town, but there were three garrisons. He continued to the Peloponnese, where he reestablished his power in 294.
The real object of Demetrius' return to Europe, however, was not Greece, but Macedonia. In 298 Cassander had died. Only a few people mourned for the man who had provoked the Second Diadoch War, massacred the Macedonian royal house, and garrisoned Greece. He was succeeded by his son Philip IV, who died within two months (of natural causes). His two brothers now divided the kingdom: Antipater received the western and Alexander the eastern half (the river Axios being the border). As was to be expected, they immediately started to quarrel. Alexander felt threatened, and in 294 invited two men to come to his assistance: Demetrius and Pyrrhus, a prince who had been made king of Epirus by a coup that had been financed by Ptolemy (297).
Pyrrhus was the first to intervene. In 294, he invaded Macedonia, restored the balance of power between the two brothers, and received Ambracia, a town in western Greece that had been occupied by the Macedonians, in return. It became the new capital of Epirus.
By now, Demetrius had returned from the Peloponnese and was entering Macedonia. King Alexander went out to greet him and thank him (for nothing), and tried to kill his powerful neighbor. However, Demetrius discovered the plan, and had instead Alexander killed. Almost immediately, the Macedonian army proclaimed Demetrius king (text). He went on to attack the second brother, Antipater, who fled to Lysimachus.
However, Demetrius had to pay for his success. He had given up positions in Asia, which were immediately seized by Lysimachus, Seleucus, and Ptolemy. The first one helped himself to the towns on the west coast of what is now called Turkey, the second one seized large parts of Cilicia, and the third one occupied Cyprus, Lycia and eastern Cilicia (291-287). Demetrius did not really care, and conquered the remaining parts of Greece. The only parts that he did not possess were Sparta in the south and Aetolia in the west.
When Demetrius invaded the last-mentioned country, Pyrrhus came to the help of the Aetolians and defeated one of the enemy's generals. However, when he decided that he was now strong enough to invade Macedonia, he was defeated (289). In the last weeks of the year, the two kings signed a peace treaty.
Although Demetrius' kingdom was smaller than that of Lysimachus, Ptolemy or Seleucus, he was the strongest of the four monarchs: his army was of the size of that of the kings Philip and Alexander the Great, and his navy was stronger. Moreover, he could count on the Greeks. As usual, power provoked resistance, and his three competitors allied themselves against Demetrius, and agreed to attack him, to prevent an attack by him. Ptolemy would send his navy into the Aegean Sea, and Lysimachus was to invade Macedonia, together with Pyrrhus. Seleucus, whose territories did not border on Demetrius', gave moral support.
At this moment, the Macedonians revolted against their king (288). It is not exactly clear why, but it is tempting to suppose that they were shocked by Demetrius' oriental court and the forced conscription, which must have been a disappointment after the quiet last years of Cassander.
The revolt must have broken Demetrius, who knew that he would lose his kingdom if he stayed in Macedonia. Therefore, he installed his son Antigonus Gonatas as governor of Greece, and decided to launch an all-out attack on the east.
It was a desperate gamble, but he hoped to defeat the troops of Lysimachus in Turkey, which would force him to look to the east instead of Macedonia. If Demetrius could also defeat Seleucus, he could break through to the eastern satrapies, gather troops, and come back with a large force. During the Second Diadoch War, Eumenes had done the same, and had caused a lot of trouble to Antigonus.
The first stage of this campaign was a success: his navy expelled the fleet of Ptolemy out of the Aegean Sea, and Demetrius made an unopposed landing in Asia, where he captured important towns like Miletus and Sardes (287). Now, he emulated Alexander and started his march against the king of Asia. However, his soldiers, who won a victory over Seleucus in Cilicia, felt that they were expatriated under false pretenses, and became unquiet. Even worse, Lysimachus' general, his son Agathocles, dogged Demetrius' army. Late in 286, most of his men deserted him, and ultimately, Demetrius was forced to surrender.
He was taken captive by Seleucus and treated kindly. His host may have wanted to use his father-in-law as a tool against Lysimachus, but Demetrius was unable to wait. The last of the generation of warrior kings drank himself to death (283). The future belonged to the more stable monarchies of Ptolemy and Seleucus. But his immediate inheritance was a war between Lysimachus and Pyrrhus: who was to succeed him as king of Macedonia?