Prince of one of the Alexandrian successor states, Pyrrhus was dethroned at the age of 17 when he left his Kingdom to attend a wedding. A clever and vigorous mind, he soon recaptured his Kingdom with the help of the Ptolemaic kings of Egypt. By 286 he had as well deposed his former brother-in-law and took control over the Kingdom of Macedonia, which he as quickly lost.
In 281 the Greek city of Tarentum fell out with Rome, and was faced with a Roman attack and certain defeat. Rome had already made itself into a major power, and poised to subdue all the Greek cities in Magna Graeca or Southern Italy. The Tarentines begged Pyrrhus to intervene and save them from Roman conquest.
Pyrrhus was encouraged to aid the Tarentines by an oracle from Delphi. His goals were not, however, selfless. He recognized the possibility of carving out an empire for himself in Italy. He made an alliance with Ptolemy Ceraunus, King of Macedon and his most powerful neighbor, and arrived in Italy in 280. He entered Italy with over 23,000 infantry, slingers and archers, 3,000 cavalry, and 19 elephants in a bid to subdue the Romans.
Due to his superior cavalry and his elephants he defeated the Romans at Heraclea under their consul Publius Valerius Laevinus in 281 BC. He then offered a peace treaty, which was rejected by the Romans. When Pyrrhus invaded Apulia (279 BC), the two armies met in the Battle of Asculum (279) where Pyrrhus won a very costly victory.
In 278, Pyrrhus received two offers simultaneously. The Greek cities in Sicily asked him to come and drive out Carthage (with Rome, one of the two great powers in the Western Mediterranean). At the same time, the Macedonians, whose King Ceraunus had been killed by invading Gauls, asked Pyrrhus to ascend the throne of Macedon. Pyrrhus decided that Sicily offered him a greater opportunity, and transferred his army there.
Pyrrhus was proclaimed king of Sicily. He was already making plans for his son Helenus to inherit the kingdom of Sicily, and his other son Alexander to be given that of Italy. In 277 Pyrrhus captures Eryx, the strongest Carthaginian fortress in Sicily. This prompted the rest of the Carthaginian-controlled cities to defect to Pyrrhus.
In 276, Pyrrhus negotiated with the Carthaginians. Although they were inclined to come to terms with Pyrrhus, supply him money and send him ships once friendly relations were established, he demanded that Carthage abandon all Sicily and make the Libyan Sea a boundary between themselves and the Greeks. Meanwhile, he had begun to display despotic behavior towards the Sicilian Greeks, and soon Sicilian opinion became inflamed against him. Though he defeated the Carthaginians in another battle, he was forced to abandon Sicily and return to Italy.
Eventually, he was defeated at Beneventum (275 BC) in Sicily, being trumped by the discipline and new tactics of the Roman Republican Legions.
Pyrrhus abandoned the campaign in Italy and returned to Epirus. Attacking King Antigonus II Gonatas he won an easy victory and seized the Macedonian throne.
In 272, Cleonymus, a Spartan of royal blood but hated in Sparta, asked Pyrrhus to attack Sparta and place him in power. Pyrrhus agreed to the plan, intending to win control of the Peloponnese for himself, but unexpectedly strong resistance thwarted his assault on Sparta. He was immediately offered an opportunity to intervene in a civic dispute in Argos. Entering the city with his army by stealth, he found himself caught in a confused battle in the narrow city streets. During the confusion, an old woman watching from a rooftop threw a roofing tile and killed him.
While he was a mercurial and often restless leader, and not always a wise king, he was considered one of the greatest military commanders of his times, ranked by Hannibal himself to be the second greatest commander the world had seen after Alexander the Great. As a general, Pyrrus' greatest political weaknesses were the failure to maintain focus, the failure to maintain a strong treasury at home (many of his soldiers were costly mercenaries), and the fact that his Macedonian-style Phalanx system was simply no match for the new tactics developed by the Romans, based on their legions.
His name is famous for the phrase "Pyrrhic victory" which refers an exchange after the Battle of Ausculum. In response to congratulations for winning a costly victory over the Romans, he is reported to have said: "One more victory like this will be the end of me."