The Battle of Ipsus (Ancient Greek: Ἱψός) was fought between the successors of Alexander the Great (referred to as the Diadochi) in 301 BC near the town of Ipsus in Phrygia.
Antigonus I Monophthalmus, the Greek Macedonian ruler of large parts of Asia, and his son Demetrius were pitted against the coalition of three other successors of Alexander: Cassander, ruler of Macedon; Lysimachus, ruler of Thrace; and Seleucus I Nicator, ruler of Babylonia and Persia.
Background
In the aftermath of the Second War of the Diadochi (315 BC), the aging satrap Antigonus I Monophthalmus had been left in undisputed control of the Asian territories of the Macedonian empire (Asia Minor, Syria and the vast eastern satrapies). This left Antigonus in prime position to claim overall rule over the Macedonian empire. Antigonus's growing power alarmed the other major Successors, resulting in the eruption of the Third War of the Diadochi in 314 BC, in which Antigonus faced a coalition of Cassander (ruler of Macedonia), Lysimachus (ruler of Thrace) and Ptolemy (ruler of Egypt). This war ended in a compromise peace in 311 BC, after which Antigonus attacked Seleucus, who was attempting to re-establish himself in the eastern Satrapies of the empire. The resulting Babylonian War lasted from 311 to 309 BC, and resulted in defeat for Antigonus, allowing Seleucus to re-claim the satrapy of Babylonia and overlordship of the territories to the east.
While Antigonus was distracted elsewhere, Ptolemy had been expanding his power into the Aegean Sea and to Cyprus. Antigonus thus resumed the war with Ptolemy in 308 BC, beginning the Fourth War of the Diadochi. Antigonus sent his son Demetrius to regain control of Greece, and in 307 BC he took Athens, expelling Demetrius of Phaleron, Cassander's governor, and proclaiming the city free again. Demetrius then turned his attention to Ptolemy, invading Cyprus and defeating Ptolemy's fleet at the Battle of Salamis-in-Cyprus. In the aftermath of this victory, Antigonus and Demetrius both assumed the crown of Macedon, in which they were shortly followed by Ptolemy, Seleucus, Lysimachus, and eventually Cassander.
In 306, Antigonus attempted to invade Egypt, but storms prevented Demetrius's fleet from supplying him, and he was forced to return home. With Cassander and Ptolemy both weakened, and Seleucus still occupied by attempting to assert his control over the East, Antigonus and Demetrius now turned their attention to Rhodes, which was besieged by Demetrius's forces in 305 BC. 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 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 thus returned to Greece and set about liberating the cities of Greece, expelling Cassander's garrisons, and the pro-Antipatrid oligarchies. This occupied much of Demetrius's efforts in 303 and 302 BC.
Seeing that Demetrius's war effort was aimed at destroying his power in Greece, and ultimately in Macedonia, Cassander tried to come to terms with Antigonus. However, Antigonus rejected these advances, intent on forcing Cassander's complete surrender. Cassander therefore held counsel with Lysimachus, and they agreed on a joint strategy that included sending envoys to Ptolemy and Seleucus, asking them to join in combatting the Antigonid threat. Seeking to take the initiative, Cassander sent a significant portion of the Macedonian army under Prepelaus to Lysimachus, which was to be used in joint operations in Asia Minor. Meanwhile, Cassander took the rest of the Macedonian army into Thessaly to confront Demetrius.
Prelude
Lysimachus crossed over the Hellespont in 302 BC, intending to take advantage of Antigonus's absence in Syria by overrunning Asia Minor. The cities of Lampsakos and Parion submitted to him, but he had to storm Sigeion, after which he installed a garrison there. He then sent Prepelaus with 7,000 men to attack Aeolis and Ionia, while he besieged Abydos. This siege was unsuccessful however, since Demetrius sent the city reinforcements from Greece by sea. Lysimachus instead went on to win over Hellespontine Phrygia, and then captured the major administrative centre of Synnada. Meanwhile, Prepelaus captured Adramyttion, Ephesos, Teos, and Colophon; he could not however capture Erythrae or Clazomenae, again due to sea-borne reinforcements. Finally, Prepelaus moved inland and captured Sardis, another major administrative centre.
When Antigonus received news of the invasion, he abandoned preparations for a great festival to be held in Antigoneia, and quickly began to march his army northwards from Syria, through Cilicia, Cappadocia, Lycaonia, and into Phrygia. Lysimachus, hearing of the approach of Antigonus's army, held counsel with his officers, and decided to avoid open battle until Seleucus's arrival. The allies thus defended their camp with entrenchments and palisades, and when Antigonus arrived offering battle, they remained within the camp. Antigonus therefore moved to cut off the allies' provisions, forcing Lysimachus to abandon the camp and make a night-time march of some 40 miles to Dorylaion. There, the allies built a new, triple-palisaded camp amongst the hills, with relatively easy access to food and water. Antigonus followed closely behind, and laid siege to the allied camp, bringing up catapults for the assault. Lysimachus sent sorties to try to disrupt the siege-works, but the Antigonid forces always ended with the upper hand in ensuing skirmishes. With the siege works nearing completion and food running low, Lysimachus decided to abandon the camp, and marched away during a night-time storm. Antigonus again attempted to follow, but as winter approached with further rain, conditions became difficult, and he abandoned pursuit and dispersed his men into winter quarters instead. The allied army marched on into Bithynia and went into winter quarters in and around the city of Heraclea.
Whilst settling his army for the winter, Antigonus heard the news that Seleucus was en route from the eastern satrapies to support Lysimachus. He therefore dispatched messengers to Demetrius, ordering him to bring his army over to Asia to reinforce the Antigonid forces. Demetrius had in the meantime continued his campaign in Greece, and although Cassander had blocked the land-passes, Demetrius had entered Thessaly by sea. There had followed a somewhat inconsequential campaign of manoeuvre between the two armies in Thessaly, before Demetrius received his father's messages asking for reinforcements. Demetrius thus hastily arranged a truce with Cassander, and took his army by sea across the Aegean to Ephesos. He recaptured Ephesos, and marched north to the Hellespont, where he established a strong garrison and fleet to prevent European reinforcements reaching the allied army in Asia. Demetrius then also dispersed his army into winter quarters.
In the absence of Demetrius, Cassander now felt able to send further reinforcements to Lysimachus, under the command of his brother, Pleistarchus. Since Demetrius was guarding the easy crossing points at the Hellespont and the Bosphorus, Pleistarchus attempted to ship his men directly across the Black Sea to Heraclea, using the port of Odessos. The men had to be sent in batches due to a lack of ships, and although the first batch arrived safely, the second shipment was intercepted by Demetrius's fleet, and the third wrecked in a storm. Pleistarchus himself narrowly survived the wreck of his command ship, eventually being carried to Heraclea to recuperate over the winter. Similarly, the concentration of Antigonid forces in Asia now made Ptolemy feel secure enough to bring an army out of Egypt to try to conquer Coele Syria. He captured a number of cities, but while laying siege to Sidon, he was brought false reports of an Antigonid victory, and told that Antigonus was marching south into Syria. He thus garrisoned the cities he had captured, and retreated into Egypt. At around the same time, Seleucus appears to have finished his march from the east, arriving in Cappadocia with his army, which he then sent into winter quarters.
Diodorus completes book XX of his Library at this point, saying that he will describe the battle between the Kings at the start of the next book. However, only fragments remain of books XXI onwards, and although some fragments of his description of the battle do remain, they do not form a coherent narrative. In his description of the battle, Plutarch does not describe the preliminary manoeuvring that must have occurred in 301 BC before the battle, so it is unclear how events unfolded. Lysimachus and Seleucus were probably anxious to bring Antigonus to battle, since their respective power-centres in Thrace and Babylon were vulnerable in their prolonged absence. The armies eventually met in battle around 50 miles north-east of Synnada, near the village of Ipsus. Antigonus was aware of Ptolemy's raid on Syria the previous year, and thus would have been loath to be cut off from Syria and his capital in Antigonia, and thus moved to intercept the allied army. The exact location of the battle is unknown, but it occurred in a large open plain, well-suited for both the allied preponderance of elephants and the Antigonid superiority in cavalry numbers and training.
Opposing forces
Antigonids
According to Plutarch, Antigonus's army before the battle numbered around 70,000 infantry, 10,000 cavalry and 75 war elephants. The majority of this number were presumably supplied by Antigonus's army that marched from Syria, since Demetrius's army in Greece had no elephants and only 1,500 cavalry. Diodorus claims that Demetrius's had approximately 56,000 infantry in Greece (8,000 Macedonian phalangites, 15,000 mercenaries, 25,000 troops from Greek cities and 8,000 light troops), but it is unclear what proportion of this infantry accompanied him to Asia. Based on other battles between the Diadochi, modern experts estimate that of the 70,000 Antigonid infantry, perhaps 40,000 were phalangites and 30,000 were light troops of various kinds.
Allies
Plutarch gives a total of 64,000 infantry for the allies, with 10,500 cavalry, 400 elephants and 120 scythed chariots. Diodorus claims that Seleucus brought 20,000 infantry, 12,000 cavalry (including mounted archers), 480 Indian elephants and more than a hundred scythed chariots with him from the eastern satrapies. Those war elephants were given to Seleucus as a gift from Mauryan emperor Chandragupta Maurya after Seleucid Mauryan war and eventually forming a marriage alliance between two empires. The numbers of elephants and chariots supposed to be present at the battle are therefore relatively consistent between these sources. However, Seleucus's cavalry component according to Diodorus is alone larger than Plutarch's claims for the whole allied cavalry, and Lysimachus must have had at least some cavalry; he sent at least 1,000 horsemen with Prepelaus the previous year. Modern experts thus estimate the total number of allied cavalry at 15,000. Of the 44,000 non-Seleucid infantry, it is unclear what proportion were supplied by Cassander and Lysimachus respectively. Cassander sent 12,000 men under Pleistarchus, of which two-thirds were lost in crossing the Black Sea, but it is not clear how many men were in the initial dispatch of troops sent under Prepelaus. Modern experts estimate that, of the allies' total infantry, perhaps 30,000–40,000 were phalangites, with the remainder being light troop types.