Alexander the Molossian, the Epirote king called to the aid of Taras, had claimed a victory over the Messapians between 333 BCE and 330 BCE.

The Messapians had joined forces with the Tarentines ater his death in 330 BCE to face an even greater force, that of Rome.

Taranto, attacked by the Lucanians in 304 BCE, asks for the help of Agathocles, who arrives in southern Italy and takes control of Bruttium (present-day Calabria), but is later called back to Syracuse.

Cleonymus of Sparta establishes an alliance with Taranto against the Lucanians in 303 BCE - 302 BCE, and fights against them.

To help Taranto against the Lucani, Cleonymus had gone as mercenary leader to southern Italy in 303 BCE with the backing of the Spartan administration..

There are two different accounts of his Italian expedition; one written by Diodorus Siculus and one by Livy, but the relations between the two sources are unclear.

The historian Thomas Lenschau supposes that they describe two different campaigns of Cleonymus: that one described by Diodorus Siculus would have taken place in 303 BCE and that one described by Livy in 302 BCE.

According to Diodorus Siculus, Cleonymus raises such a large army that the Lucani immediately conclude peace.

Then the Spartan prince takes the city of Metaponto and sails to Corcyra, which island he also quickly captures.

Learning that Taranto and other cities have broken with him, he sails back and is at first successful, but then he is defeated at a night attack.

As many of his ships are destroyed by a storm at the same time, he has to withdraw to Corcyra ion 303 or 302 BCE).

Probably in the next year (302 BCE) Cleonymus returns to Italy and—according to Livy—first conquers a city called Thuriae, location unknown, but Roman armies force him back to his ships.

The alliance with Taras and with Cleonymus of Sparta is essentially an anti-Roman campaign.

Thus, towards the end of the fourth century, Rome had become a common enemy for both the Iapygians and the Tarentines, even as far as ending the prolonged battles and causing them to make an alliance.

Cleonymus, expelled from southern Italy, sails to the north across the Adriatic Sea to land at the coast of the Veneti.

The Veneti have recurring fights with the Celtic peoples who occupy most of Northern Italy, but also have peaceful relations with the Cenomani Celts who have settled in the region of Brescia and Verona; they will eventually absorb them.

From the mouth of the Meduacus (now Brenta River) he sails upstream to the country of Patavium (now Padua) and raids the nearby villages, but the natives defeat him and he suffers great losses —allegedly four fifths of his ships are destroyed—and Cleonymus has to leave the territory of Patavium.

It is unknown how his campaign ended.

Pyrrhus's retreat from Italy proves unlucky for Antigonus II Gonatus of Macedon.

Returning to Epirus with an army of eight thousand foot and five hundred horse, he was in need of money to pay them.

This had encouraged him to look for another war, so the next year, after adding a force of Gallic mercenaries to his army, he invaded Macedonia with the intention of filling his coffers with plunder.

The campaign goes better than expected.

Making himself master of several towns and being joined by two thousand deserters, his hopes start to grow and he goes in search of Antigonus, attacking his army in a narrow pass and throwing it into disorder.

Antigonus's Macedonian troops retreat, but his own body of Gallic mercenaries, who have charge of his elephants, stand firm until Pyrrhus's troops surround them, whereupon they surrender both themselves and the elephants.

Pyrrhus now chases after the rest of Antigonus's army which, demoralized by its earlier defeat, declines to fight.

As the two armies face each other, Pyrrhus calls out to the various officers by name and persuades the whole body of infantry to desert.

Antigonus escapes by concealing his identity.

Pyrrhus now takes control of upper Macedonia and Thessaly while Antigonus holds onto the coastal towns.

Pyrrhus now wastes his victory.

Taking possession of Aegae, the ancient capital of Macedonia, he installs a garrison of Gauls, who greatly offend the Macedonians by digging up the tombs of their kings and leaving the bones scattered about as they search for gold.

He also neglects to finish off his enemy.

Leaving Antigonus in control of the coastal cities, he contents himself with insults.

He calls Antigonus a shameless man for still wearing the purple, but he does little to destroy the remnants of his power.

Pyrrhus, suddenly abandoning Macedonia in 272 BCE for an invasion of southern Greece,  launches an unsuccessful attack on Sparta to restore Cleonymus to the kingship.

Antigonus, although he retains only a few Macedonian cities, follows Pyrrhus when the latter marches into the Peloponnese.

Pyrrhus is killed, however, in a night skirmish in the streets of Argos, struck to the ground by a tile hurled down by a woman watching from the roof; …

…thereby assuring Gonatus' control over Macedonia.

He is now also the chief of the Thessalian League and on good terms with neighboring Illyria and Thrace.

The son of the brilliant Demetrius I Poliorcetes and himself a man of high character, ability, and culture, Gonatus secures his position in the north of Greece and …

…by keeping Macedonian occupation forces in the three “shackles” of Hellas: the cities of Corinth, …

…Chalcis on Euboea, and …

…Demetrias in Thessaly.