Pyrrhus or Pyrrhos (Greek: Πύρρος, Pyrros; 319/318 BC-272 BC) was a Greek general and statesman of the Hellenistic era. He was king of the Greek tribe of Molossians, of the royal Aeacid house (from ca. 297 BC), and later he became King of Epirus (306-302, 297-272 BC) and Macedon (288-284, 273-272 BC). He was one of the strongest opponents of early Rome. Some of his battles, though successful, cost him heavy losses, from which the term "Pyrrhic victory" was coined. He is the subject of one of Plutarch's Parallel Lives.
Pyrrhus was the son of Aeacides and Phthia, a Thessalian woman, and a second cousin of Alexander the Great (via Alexander's mother, Olympias). Pyrrhus was only two years old when his father was dethroned, in 317 BC, his family taking refuge with Glaukias, king of the Taulantians, one of the largest Illyrian tribes. Pyrrhus was raised by Beroea, Glaukias's wife and a Molossian Aeacidae dynasty.
Glaukias restored Pyrrhus to the throne in 306 BC until the latter was banished again, four years later, by his enemy, Cassander. Thus, he went on to serve as an officer, in the wars of the Diadochi, under his brother-in-law Demetrius Poliorcetes. In 298 BC, Pyrrhus was taken hostage to Alexandria, under the terms of a peace treaty made between Demetrius and Ptolemy I Soter. There, he married Ptolemy I's stepdaughter Antigone (daughter of Berenice I of Egypt, Ptolemy's mistress, and a Macedonian noble) and, in 297 BC, with Ptolemy I's financial and military aid, restored his kingdom in Epirus and had Neoptolemus II - puppet of the now-deceased Seleucus and Pyrrhus' co-ruler for a short while - murdered. Through his marriage to Antigone, she bore him a son called Ptolemy and possibly a daughter called Olympias. 
In 295 BC, Pyrrhus transferred the capital of his kingdom to Ambrakia (modern Arta). Next, he went to war against his former ally and brother-in-law Demetrius, and, by 286 BC, he had taken control over the kingdom of Macedon. Pyrrhus was driven out of Macedon by Lysimachus in 284 BC.
Struggle with Rome
In 281 BC, the Greek city of Tarentum, in southern Italy, fell out with Rome and was faced with a Roman attack and certain defeat. Rome had already made itself into a major power, and was poised to subdue all the Greek cities in Magna Graecia. The Tarentines asked Pyrrhus to lead their war against the Romans.
Pyrrhus was encouraged to aid the Tarentines by the oracle of 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 BC.
He entered Italy with an army consisting of 3,000 cavalry, 2,000 archers, 500 slingers, 20,000 infantry and 20 war elephants in a bid to subdue the Romans. The elephants had been loaned to him by Ptolemy II, who had also promised 9,000 soldiers and a further 50 elephants to defend Epirus while Pyrrhus and his army were away.
Due to his superior cavalry and his elephants, he defeated the Romans, led by Consul Publius Valerius Laevinus, in the Battle of Heraclea in 280 BC. There are conflicting sources about casualties. Hieronymus of Cardia reports the Romans lost about 7,000 while Pyrrhus lost 3,000 soldiers, including many of his best. Dionysius gives a bloodier view of 15,000 Roman dead and 13,000 Greek. Several tribes including the Lucani, Bruttii, Messapians, and the Greek cities of Croton and Locri joined Pyrrhus. He then offered the Romans a peace treaty which was eventually rejected. Pyrrhus spent winter in Campania.
When Pyrrhus invaded Apulia (279 BC), the two armies met in the Battle of Asculum where Pyrrhus won a very costly victory. The consul Publius Decius Mus was the Roman commander, and his able force, though defeated, broke the back of Pyrrhus' Hellenistic army, and guaranteed the security of the city itself. The battle foreshadowed later Roman victories over more numerous and well armed successor state military forces and inspired the term "Pyrrhic victory", meaning a victory which comes at a crippling cost. At the end, the Romans had lost 6,000 men and Pyrrhus 3,500 but, while battered, his army was still a force to be reckoned with.
Ruler of Sicily
In 278 BC, Pyrrhus received two offers simultaneously. The Greek cities in Sicily asked him to come and drive out Carthage, which along with Rome was one of the two great powers of 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 Italy. In 277 Pyrrhus captured Eryx, the strongest Carthaginian fortress in Sicily. This prompted the rest of the Carthaginian-controlled cities to defect to Pyrrhus.
In 276 BC, 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 of Sicily and make the Libyan Sea a boundary between themselves and the Greeks. The Greek cities of Sicily opposed making peace with Carthage because the Carthaginians still controlled the powerful fortress of Lilybaeum, on the western end of the island. Pyrrhus eventually gave in to their proposals and broke off the peace negotiations. Pyrrhus' army then began besieging Lilybaeum. For two months he launched unsuccessful assaults on the city, until finally he realised he could not mount an effective siege without blockading it from the sea as well. Pyrrhus then requested manpower and money from the Sicilians in order to construct a powerful fleet. When the Sicilians became unhappy about these contributions he had to resort to compulsory contributions and force to keep them in line. These measures culminated in him proclaiming a military dictatorship of Sicily and installing military garrisons in Sicilian cities.
These actions were deeply unpopular and soon Sicilian opinion became inflamed against him. Pyrrhus had so alienated the Sicilian Greeks that they were willing to make common cause with the Carthaginians. The Carthaginians took heart from this and sent another army against him. This army was promptly defeated. In spite of this victory Sicily continued to grow increasingly hostile to Pyrrhus, who began to consider abandoning Sicily. At this point Samnite and Tarentine envoys reached Pyrrhus and informed him that of all the Greek cities in Italy only Tarentum had not been conquered by Rome. Pyrrhus made his decision and departed from Sicily. As his ship left the island, he turned and said to his companions: "What a wrestling ground we are leaving, my friends, for the Carthaginians and the Romans."
Retreat from Italy
While Pyrrhus had been campaigning against the Carthaginians, the Romans rebuilt their army by calling up thousands of fresh recruits. When Pyrrhus returned from Sicily, he found himself vastly outnumbered against a superior Roman army. After the inconclusive Battle of Beneventum in 275 BC Pyrrhus decided to end his campaign in Italy and return to Epirus which resulted in the loss of all his Italian holdings. Before leaving Italy Pyrrhus sent requests for military and financial assistance to Greece and Macedon, as well as to the Hellenic empires of the Ptolemaic and Seleucid dynasties. These appeals were all in vain.
Last wars and death
Though his western campaign had taken a heavy toll on his army as well as his treasury, Pyrrhus went to war yet again. Attacking King Antigonus II Gonatas, he won an easy victory and seized the Macedonian throne.
In 272 BC, Cleonymus, a Spartan of royal blood who was hated among fellow Spartans, 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 unexpected 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 Argead woman watching from a rooftop threw a roofing tile which stunned him, allowing an Argive soldier to behead him.
The same year, upon hearing the news of Pyrrhus' death, the Tarentinians surrendered to Rome.
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 time. Plutarch records that Hannibal ranked Pyrrhus as the greatest commander the world had ever seen, though Appian gives a different version of the story, in which Hannibal placed him second after Alexander the Great.
Pyrrhus was also known to be very benevolent. As a general, Pyrrhus' greatest political weaknesses were his failures to maintain focus and to maintain a strong treasury at home (many of his soldiers were costly mercenaries).
His name is famous for the term "Pyrrhic victory" which refers to an exchange at the Battle of Asculum. In response to congratulations for winning a costly victory over the Romans, he is reported to have said: "One more such victory will undo me!" (In Greek: Ἂν ἔτι μίαν μάχην νικήσωμεν, ἀπολώλαμεν.)
Pyrrhus and his campaign in Italy was effectively the only chance for Greece to check the advance of Rome towards domination of the Mediterranean world. Rather than banding together, the various Hellenic powers continued to fight among themselves, sapping the financial and military strength of Greece and to a lesser extent, Macedon and the greater Hellenic world. By 197 BC, Macedonia and the southern Greek city-states were under the control of Rome and the age of Greece as a major power was well and truly over. In 188 BC, the Seleucid Empire was forced to cede most of Asia Minor to Rome and Egypt was left as the last vestige of Alexander's Empire.
Pyrrhus wrote Memoirs and several books on the art of war. These have since been lost, although, according to Plutarch, Hannibal was influenced by them, and they received praise from Cicero.