Seleucus had in 302 BCE joined the anti-Antigonus confederation led by Cassander and Lysimachus.

Ceding the claim on his Indian province to Chandragupta in exchange for an elephant corps, he has led his army (including the elephants) across half of Asia to link up with the coalition.

The united armies of Lysimachus and Seleucus engage the forces of Antigonus and Demetrius at Ipsus in Phrygia in 301 BCE.

Although the combined strength of Seleucus and Lysimachus in troops is only slightly inferior to the seventy thousand foot soldiers and ten thousand horses of Antigonus, it is the allies' superiority in elephants, courtesy of Seleucus, that prove invaluable for victory.

The Indian elephants prevent Demetrius, who has pursued too far after defeating the opposing cavalry, from returning to rescue his father.

The eighty-one-year-old Antigonus is killed by a javelin, Demetrius flees, and the greater part of Asia Minor is added to the European possessions of Lysimachus, who has shouldered most of the burden of the campaign.

The allied victory ends any plans the Antigonid court may have had of reuniting Alexander's empire.

Antigonus's kingdom is divided up, with most ending up in the hands of new kingdoms under Lysimachus and Seleucus.

The victors largely follow Antigonus's precedent and have themselves named as kings, but they do not claim power over the erstwhile empire of Alexander nor each other.

Instead, these kings establish a troubled (and in the end failed) modus vivendi with each other, and accept their kingdoms as separate realms.