In the spring of 315, the Third War of the Diadochi broke out. Antigonus Monophthalmus, who controled great parts of Asia between the Hellespont and the Hindu Kush, had to fight against a coalition of Cassander of Macedonia, Lysimachus of Thrace, Ptolemy of Egypt, and Seleucus, who had once been satrap of Babylonia but had been expelled by Antigonus. One of Antigonus' diplomatic initiatives was the proclamation of the independence of the Greek towns, a measure that would seriously handicap Cassander.
The story is told in the World History of Diodorus of Sicily (19.61-62). The present translation was made by M.M. Austin.
Antigonus proclaims the "Freedom of the Greeks"
[19.61.1] Antigonus established friendship with Alexander son of Polyperchon, who had joined him. He also summoned a general assembly of his troops and of the resident foreigners and accused Cassander, invoking the execution of Olympias and the fate of Roxane and the king.note[Olympias, the mother of Alexander the Great, had been murdered in 315.]
[19.61.2] Antigonus added that Cassander had forced Thessalonicanote[Thessalonica (351-294) was the half-sister of Alexander the Great, and married to Cassander in 315. The city Thessaloniki is called after this lady.] to marry him, that he was manifestly seeking to appropriate the throne of Macedonia, and also that he had settled the Olynthians, the worst enemies of the Macedonians, in the city he named after himselfnote[In 316, Cassander had refounded Potideia, and had settled people of the neighboring towns in this city. Cassandreia was meant as the new capital of Macedonia.] and had restored Thebes which the Macedonians had razed to the ground.note[Alexander the Great had destroyed Thebes in 335 (text).]
[19.61.3] As the crowd shared his indignation he moved a resolution that Cassander should be regarded as an enemy, unless he destroyed the two cities, released from captivity the king and Roxane his mother and restored them to the Macedonians, and in general obeyed Antigonus, the appointed general who had received the supervision of the kingdom. All the Greeks should be free, exempt from garrisons, and autonomous.
The soldiers carried the motion and Antigonus dispatched messengers in every direction to announce the resolution.
[19.61.4] He calculated as follows: the Greeks' hopes for freedom would make them willing allies in the war, while the generals and satraps in the eastern satrapies, who suspected Antigonus of seeking to overthrow the kings who had succeeded Alexander, would change their minds and willingly submit to his orders when they saw him clearly taking up the war on their behalf.
[19.61.5] Having done this he gave 500 talents to Alexander and dispatched him to the Peloponnese with great hopes for the future.
He sent for ships from the Rhodians and, having equipped most of those that had been built, he set sail against Tyre. Through his command of the sea he prevented grain being imported to the city and maintained the blockade for a year and three months. The besieged were starved into submission. Ptolemy's soldiers he allowed to go away with their possessions, and after receiving the surrender of the city he placed there a garrison to defend it.
[19.62.1] While this was happening, Ptolemy heard of the resolution concerning the freedom of the Greeks which the Macedonians with Antigonus had passed, and drafted a proclamation in much the same words to convey to the Greeks that he cared no less for their autonomy than did Antigonus.
[19.62.2] Each side saw that to gain the goodwill of the Greeks would carry no little weight, and so they vied with each other in conferring favors on them.