Alexander the Great died in Babylon in 323 BC without a viable heir and without a designated successor. What followed was not a transition but a fracture. His generals — the Diadochi, or 'Successors' — began maneuvering immediately for control of the empire he had built. Perdiccas inherited the main Macedonian army and claimed the title of regent of the Asiatic Empire. He also pursued a marriage to Alexander's sister Cleopatra of Macedon, which would have given him a bloodline claim to the Macedonian throne itself. That was too much for the other successors. A coalition formed against Perdiccas, and Craterus — one of the most respected figures from Alexander's campaigns — marched an army toward Asia to confront him.

Perdiccas sent Eumenes and Neoptolemus jointly to the Hellespont to prevent Craterus from crossing into Asia. The two commanders were not a natural partnership. Neoptolemus resented being subordinate to a Greek administrator with no background in Macedonian military culture. Before the armies had even engaged, Neoptolemus deserted — taking a few hundred cavalry with him and joining Craterus on the other side of the strait. It was a betrayal that seemed to doom Eumenes: now he faced both Craterus's formidable veteran infantry and the defecting Neoptolemus, while commanding a force without the prestige of either commander it faced. What Eumenes had, however, was cavalry — more numerous and better organized than Craterus had anticipated.

When the armies met, both sides deployed in the classical Macedonian formation: phalanx in the center, cavalry on the wings. Craterus's infantry phalanx was composed of veteran Macedonians who had fought under Alexander — hardened soldiers whose discipline and experience made them formidable. Eumenes' infantry was weaker. He compensated by entrusting his cavalry to Phoenix of Tenedos and Pharnabazus III — the former Persian satrap of Phrygia — and kept his own Macedonian horsemen away from Craterus deliberately, knowing they might hesitate to charge a general they revered. The Asiatic cavalry did not hesitate. They broke Craterus's horse before he could stabilize his line, and Craterus himself was killed in the confusion. On the other wing, Neoptolemus and Eumenes met in direct personal combat, and Neoptolemus died. With both commanders gone, Craterus's surrounded infantry surrendered.

Eumenes won completely and gained almost nothing. The surrendered Macedonian infantry agreed to join him — then slipped away by night to rejoin Antipater, the regent of Greece and Macedonia, who was also Craterus's father-in-law. Removing two powerful contenders from the board did not resolve the succession struggle; it merely redistributed the pieces. The Wars of the Diadochi continued for another four decades, grinding through coalitions and betrayals and battles across the ruins of what had been the largest empire the ancient world had known. Eumenes himself survived this battle but was eventually captured and executed years later, in 316 BC. The Hellespont battlefield — somewhere near the strait that separates Europe from Asia — returned to farmland and silence.

The Hellespont — known today as the Çanakkale Strait — has been a strategic crossing point for as long as armies have moved between Europe and Asia. Xerxes crossed it with his Persian army in 480 BC. Alexander himself crossed it in 334 BC at the start of his eastern campaigns. The battle of 321 BC was fought in its vicinity, the exact location unspecified in ancient sources but positioned somewhere in the low terrain of what is now northwestern Turkey near modern Çanakkale or eastern Balıkesir Province. The strait today is a major shipping lane, its shores lined with monuments to more recent conflicts — the Gallipoli battlefields of 1915–1916 lie just to the west. The Diadochi fought here when the earth above them was already old.