Cleitus was a Macedonian nobleman and soldier best known for his service as an admiral in the early years of the Wars of the Diadochi, although he was present in the army of Alexander the Great during his wars in Persia. In 324 BC Alexander sent a portion of his veteran soldiers, including Cleitus, back to Macedonia, under the command of Craterus. By the time Alexander died, in 323, Craterus had reached Cilicia, in south-east Asia Minor, and there he stopped while the future of the empire was being decided at Babylon.
One of the side-effects of Alexander’s death was the outbreak of a revolt in Greece, led by Athens (Lamian War). The Macedonian regent, Antipater, was besieged in the town of Lamia, in Thessaly, and called for help. Craterus responded by sending Cleitus to take command of the Macedonian fleet.
Athens had managed to raise and man an impressive fleet, 200 ships strong at the end of the naval campaign. Under the command of Euetion that fleet had sailed to the Hellespont, in an attempt to prevent Macedonian reinforcements reaching Europe.
In the spring of 322, Cleitus defeated the Athenian fleet at the battle of Abydos, close to the western end of the Hellespont. Euetion escaped, and Athens raised another fleet (or reinforced the survivors of Abydos). Cleitus followed, and inflicted a decisive defeat on the Athenian fleet at Amorgos, south west of the island of Samos. This defeat ended Athenian naval power, and soon allowed Craterus to reach Greece. The Greek allies were defeated at Crannon, and Athens surrendered.
Cleitus was rewarded by Antipater, who in 321 appointed him to the satrapy of Lydia (western Asia Minor). He retained that post through the first phase of the Diadochi wars. However, in 319 Antipater died (of natural causes, one of only two of the main Diadochi to do so!). Craterus was also dead, having been killed in battle. A second round of fighting soon began, between Royalists loyal to the Macedonian royal family, led by Polyperchon and Eumenes on one side, and a coalition between Antigonus, Cassander, Ptolemy and Lysimachus. Cleitus sided with the loyalists, and was almost immediately forced out of Lydia.
He was then appointed to command Polyperchon’s fleet. His most important duty was to keep open the lines of communication between Polyperchon in Greece and Eumenes in Asia Minor. Accordingly, he took his fleet to the Hellespont. Antigonus and his allies sent a fleet under Nicanor to oppose Cleitus. The resulting battle of the Bosporus (318) took place over two days. On the first day, Cleitus was victorious, apparently destroying half of Nicanor’s fleet. However, Antigonus had been able to ship some of his troops to the European shore of the Hellespont, and on the following morning launched a combined land and sea assault on Cleitus’s fleet, catching it with its ships beached. The Royalist fleet was destroyed, and although Cleitus escaped from the defeat west into Thrace, he was soon caught and killed.