King Alexander of Molossis was an uncle of Alexander the Great (the brother of Olympias). He united Epirus and accepted an invitation from the Greeks in southern Italy to defend them against the Samnites, Lucanians, and Bruttians. The Epirote achieved several successes and concluded a peace treaty with the Romans (who were also at war with the Samnites). Eventually, Alexander was defeated in 331 – more or less at the time of the foundation of Alexandria by his nephew, as the Roman historian Livy notes (History of Rome since its Foundation, 8.24).
The story is not very well-known, but is important. His intervention in Italy, which resembles that of his great-nephew Pyrrhus, prevented the Samnites from capturing the Greek towns, and ensured that the Samnite federation would always have to fight two wars at the same time – against Rome and against the Greeks. That Italy would sooner or later be united, was inevitable, but Alexander’s intervention made sure that Rome would be the master of the Apennine Peninsula.