Marble bust, usually assumed to portray King Pyrrhus of Epirus, from the Villa of the Papyri , Herculaneum,

(possibly a Roman copy from 1st century BC of a Hellenistic bronze original),

now in the National Archaeological Museum of Naples (from Wikipedia)  

Western Mediterranean after Alexander the Great (adapted from Wikipedia, my additions in white)

Pyrrhus was formally King of the Molossians and Hegemon of the neighbouring tribes of Epirus, although he is usually described as King of Epirus.  In view of the importance of his short intervention in Roman affairs in 280-75 BC, it is worth discussing his earlier history in some detail.

Pyrrhus Before 280 BC 

Epirus Before Pyrrhus

Pyrrhus’ family tree (adapted from Wikipedia, my additions in red)

As indicated in the family tree above, Pyrrhus was a second cousin of Alexander the Great (Alexander III of Macedon): Pyrrhus’ great aunt, Olympias, had married Philip II of Macedon in 357 BC.  At the time of her marriage, Olympias’ father was dead and it was her uncle, Arybbas, then King of the Molossians, who arranged this marriage (since Philip was the enemy of his enemies, the Illyrians).  It is possible that Arybbas also secured the hegemony of Epirus for Molassia at this time in return for his support.  Olympias soon secured her position at the Macedonian court by giving birth to Alexander, Philip’s first-born son, in the first year of the marriage. 

When Arybbas died in 343 BC, it was probably at Olympias’ instigation that her brother, Alexander,  (rather than one of Arybbas’ sons) became King of Molossia/ Epirus: he is usually referred to as Alexander of Epirus.  As we shall see, he served as a mercenary in Italy for a short time and was killed in battle there in 331 BC, at which point, his title passed to Pyrrhus’ father, Aeacides.  The unexpected death of Alexander the Great in 323 BC led to upheaval across the Greek world, not least in his native Macedonia, where Antipater (whom Alexander had appointed as regent in Macedonia and who had Alexander’s posthumous and homonymous son in his charge) appointed Polyperchon (another Macedoniann general) as his successor, to the chagrin of his son, Cassander.  When Antipater died in 317 BC and  broke out between Polyperchon  and Cassander, Olympias backed Polyperchon and persuaded Aeacides to join their alliance.  It was, a disastrous choice: when Cassander emerged as the victor in 317/6 BC:

1. ✴Aeacides’s soldiers mutinied and he was (temporarily) driven from Epirus, taking refuge in Aetolia; 
   

2. ✴Cassander:
   

3. •captured Olympias and executed her;
   

4. •established himself as regent for Alexander IV; and
   

5. •assumed de facto control of both Macedonia and Epirus; and
   

6. ✴Pyrrhus (who was then very young) was taken to safety in Illyria,  where he received the protection of King Glaucias, the Hegemon of Illyria (who was also opposed to Cassander).
   

Aeacides was killed in battle against Cassander in 313 BC, at which point, Cassander installed Aeacides’  older brother (Pyrrhus’ uncle) as Alcetas II.

Cassander’s position was weakened in 307 BC, when his enemy, Demetrius Poliorcetes (the son of another of of Alexander’s generals, Antigonus I) arrived in the Aegean with a fleet and established himself at Athens (which Cassander had garrisoned).  As William Greenwalt (referenced below, at p. 297) recorded:

1. “Glaucias took advantage of the situation to establish Pyrrhus on the Epirote throne in 306 BC, where he ruled with Illyrian help until [302 BC, when] he attended the wedding of one of Glaucias’ sons ... In his absence the Molossians  ... replaced him with [his cousin], Neoptolemus II.”
   

Pyrrhus’ Early Career (ca. 302 - 294 BC)

It was at this point that Pyrrhus found himself more centrally involved in the affairs of the diadochi (the rival generals who battled for control of Alexander’s empire).  We have already come across three of those who were prominent at this time:

1. ✴Cassander in Macedon; and
   

2. ✴Antigoninus I in Asia Minor, who was ably supported by his son Demetrius Poliorcetes.
   

The other three relevant figures at this time were:

1. ✴Lysimachus, ruler of Thrace;
   

2. ✴Seleucus I, ruler of Babylonia and Persia; and
   

3. ✴Ptolemy I, ruler of Egypt.
   

Battle of Ipsus and its Aftermath (301- 298 BC)

In ca. 302 BC, Glaucias entered into an alliance with Antigonus, which was cemented by the marriage of Deidamia, Pyrrhus’ older sister, to Demetrius Poliorcetes.  Thus, as William Greenwalt (referenced below, at p. 297) recorded, after his expulsion from Epirus, Pyrrhus (who was about 17) fled to Demetriua at Athens.  Thus, when Antigonus called Demetrius back to Asia to deal with an invasion by Lysimachus, Pyrrhus went with him (although Deidamia remained at Athens).  In 301 BC:

1. ✴Antigonas and Demetrius engaged with the combined armies of Lysimachus, Seleucus and Cassander at the small town of Ipsus in Anatolia; while
   

2. ✴Ptolemy made use of the distraction (or perhaps created a diversion) by invading Syria.
   

The result was decisive: Antigonus was killed, although Demetrius was able to reach his fleet at Ephesus and escape by sea.  According to Plutarch, he had placed:

1. “... his chief remaining hopes in Athens, since he had left ships and his money there, as well as his wife, Deidamia, and thought that ... no refuge could be more secure than the goodwill of Athens.   However, as he drew near the Cyclades islands, an embassy from Athens:
   

2. ✴requested that he keep away from the city, on the grounds that the people had passed a vote to admit none of the kings, and
   

3. ✴informed him that Deidamia had been sent to Megara with fitting escort and honour”, (‘Life of Demetrius’, 30: 2-3).
   

Demetrius established a new base in Greece in the territory of Megara and Corinth.  As Carlos Francis Robinson (referenced below, at p. 88) observed, although he had suffered a serious setback, he:

1. “... still possessed Cyprus and, after recovering his fleet from Athens, maintained possession of areas such as the Corinthian Isthmus and Cilicia, as well as the important ports of Tyre and Sidon.”
   

Pyrrhus, who had apparently performed well at Ipsus, had remained with Demetrius in Greece thereafter.  In ca. 299 BC, when Demetrius sailed to Syria to join his new ally, Seleucus, he left Pyrrhus  ‘in charge of Greece’.  Deidamia, who initially remained with Pyrrhus, joined Demetrius in Syria in 298 BC but died soon after her arrival.  Shortly thereafter, Demetrius made peace with King Ptolemy and demonstrated his good faith by sending Pyrrhus to Alexandria as a hostage. 

Pyrrhus at Alexandria (298-7 BC)

According to Plutarch, during his stay at Alexandria, Pyrrhus:

1. “ ... gave Ptolemy proof of his prowess and endurance [and took particular trouble to impress Ptolemy’s favourite wife], Berenicé ... Since he was orderly and restrained in his ways of living, he was selected from among many young princes as a husband for Antigone, one of the daughters of Berenicé, whom she had had by [the otherwise unknown] Philip before her marriage with Ptolemy”, (‘Life of Pyrrhus’, 4: 3).
   

Pat Wheatley and Charlotte Dunn (referenced below, at pp. 293-4) reasonably argued that Pyrrhus might well have transferred his allegiance from Demetrius to Ptolemy after the death of Deidamia.  In any event, in 297 BC:

1. “After this marriage, [Pyrrhus] was held in still greater esteem and ... [Ptolemy] brought it to pass that he was sent into Epirus with money and an army to regain his kingdom”, (‘Life of Pyrrhus’, 5: 1).
   

It seems that Pyrrhus initially agreed to share power with the incumbent, Neoptolemus II, whom he murdered shortly thereafter. 

Corcyra (295-4 BC)

According to Plutarch:

1. “In order to enlarge his interests and power, [Pyrrhus] married several wives after the death of Antigone [in ca. 295 BC]. He took to wife:
   

2. ✴a daughter of Autoleon, king of the Paeonians;
   

3. ✴Bircenna, the daughter of the Illyrian Bardyllis; and
   

4. ✴Lanassa, the daughter of King Agathocles of Syracuse, who brought as her dowry the city of Corcyra [modern Corfu], which had been captured by Agathocles”, (‘Life of Pyrrhus’, 9: 1).
   

Diodorus Siculus recorded how Agathocles had captured Corcyra in ca. 298 BC:

1. “When Cassander .. was besieging [the town] on land and sea and was on the point of capturing it, it was saved by Agathocles, king of Sicily, who set fire to the entire Macedonian fleet”, (‘Library of History’, 20: 105: 1). 
   

However it was not long before:

1. “Lanassa, who found fault with Pyrrhus for being more devoted to his barbarian wives than to her, retired to Corcyra and, since she desired a royal marriage, invited Demetrius [to the island]. Demetrius duly sailed thither, married Lanassa, and left a garrison in the city, (‘Life of Pyrrhus’, 10: 5).
   

Lanassa’s change of heart probably took place shortly after Demetrius became King of Macedonia (see below).

Macedonia (294 - 284 BC)

According to Plutarch, after the death of Cassander in 297 BC:

1. “... the eldest of his sons, Philip, reigned over the Macedonians for a only short time before he also died.  The two remaining brothers then quarrelled over the succession.  In 294 BC:
   

2. ✴one of them, Antipater, murdered his mother, Thessalonicé; and
   

3. ✴the other, Alexander, [separately] summoned to his help:
   

4. •Pyrrhus, from Epirus; and
   

5. •Demetrius, from the Peloponnese”, (‘Life of Demetrius’, 36: 1).
   

At this time, Demetrius was preoccupied with the Athenians and then the Spartans.  Pyrrhus therefore arrived in Macedonia before him and expelled Antipater, who fled to his father-in-law, Lysimachus, in Thrace.  According to Plutarch, Pyrrhus then:

1. “... demanded [the towns of] Stymphaea and Parauaea in Macedonia, ... [as well as] Ambracia, Acarnania, and Amphilochia.  The young Alexander gave way to his demands, and Pyrrhus [garrisoned his new possessions].  He then stripped Antipater of the remaining parts of his kingdom and turned them over to Alexander”, (‘Life of Pyrrhus’, 6: 2-3).
   

The result was that Macedonia was split into two:

1. ✴according to Strabo, presumably at this time, Ambracia:
   

2. “... was adorned ... by Pyrrhus, who made the place his royal residence”, (‘Geography’, 7: 7: 6); and
   

3. ✴Alexander and Antipater were subsequently reconciled at the behest of Lycymachus and shared what remained of Macedonia. 
   

Later in 294 BC, Demetrius marched on Macedonia, ostensibly in response to Alexander’s earlier request for help.  However, when Alexander came out to meet him, he murdered him, at which point Antipater fled once more to Lysimachus.  According to Plutarch (‘Life of Demetrius’, 37: 2-3), the Macedonian soldiers who had accompanied Alexander then proclaimed Demetrius king of the Macedonians.  Thus, Demetrius took at least part of Cassander’s kingdom without bloodshed and assumed the prestigious title of King of Macedonia, albeit that some of what has been Macedonian territory remained in the hands of Pyrrhus.  

Jeff Champion (referenced below, at p. 52) observed that:

1. “With his conquest of Macedonia secure, Demetrius now controlled a strong empire that included the entire Greek peninsula, with the exception of Epirus, Sparta and Messenia.”
   

He nevertheless faced revolts in Boeotia in 293 and 292 BC and, on this second occasion, he had to return to Thessaly to fight off an invasion by Pyrrhus and  his allies from Aetolia.  In 289 BC, Demetrius returned the compliment by invading Aetolia and Epirus.   Pyrrhus secured a victory against Demetrius’ general, Pantauchus, at which point Demetrius withdrew to Macedonia.  Plutarch gave an elaborate account of Pyrrhus’ performance on this occasion which ended with the claim that:

1. “This conflict did not fill the Macedonians with wrath and hate towards Pyrrhus, ... but rather led those who witnessed his exploits, [even those in the enemy army] to esteem him highly ... They likened his appearance and agility  to those of the great Alexander, ... They said that:
   

2. ✴while the other kings [copied] Alexander with their purple robes, their body-guards, the inclination of their necks and their louder tones in conversation:
   

3. ✴Pyrrhus, and Pyrrhus alone, [emulated him] in arms and action”, (‘Life of Pyrrhus’,  8: 1).
   

In fact, while Pyrrhus might have improved his reputation in this encounter, he did nothing to weaken Demetrius’ hold on Macedonia. 

However, Demetrius’ ambitions extended more widely: according to Plutarch:

1. “... his purpose was nothing less than the recovery of all the realm that had been subject to his father.  Moreover, his preparations were fully commensurate with his hopes and undertakings”, (‘Life of Demetrius’, 43: 2).
   

According to Pat Wheatley and Charlotte Dunn (referenced below, at p. 364), these preparations were well underway by 288 BC.  Unsurprisingly, Lysimachus, Seleucus, Ptolemy and Pyrrhus soon agreed to defeat Demetrius at any price:

1. ✴Ptolemy's fleet soon appeared off Greece, inciting the cities to revolt; and
   

2. ✴Lysimachus attacked Macedonia from Thrace.
   

Demetrius, who was in Greece when he became aware of the danger, left his son, Antigonus, in charge of the war there and returned to Macedonia in order to confront Lysimachus.  Pyrrhus used this opportunity to take the Macedonian city of Beroea, causing Demetrius to march in his direction and allowing Lysimachus to take Amphilipolis.  As Demetrius approached Beroa, Pyrrhus sent men to infiltrate his camp and to prompt his army to desert him.  According to Plutarch, when Demetrius became aware of:

1. “... the agitation in the camp, ... he secretly stole away ... So Pyrrhus came up, took the camp without a blow, and was proclaimed king of Macedonia”, (‘Life of Pyrrhus’, 11: 6).
   

Pyrrhus was, in fact, soon forced to share the rule of Macedonia with Lysimachus, an arrangement that lasted until 284 BC, when Lysimachus drove him out and incorporated almost all of Macedonia into his kingdom.  Thus, when the Tarantines sought his services as a mercenary commander in 280 BC, he readily accepted their offer. 

At this point, we need to make yet another digression in order to understand where the Tarentines were coming from.

Tarentum

Peninsular Italy at the outbreak of the Pyrrhic War (adapted from Wikiwand, my additions in blue)

280 BC

280/6 Pyrrhus sends Cineas ahead to Tarentum.

280/7 Pyrrhus sets sail for Italy.

280/8 Pyrrhus arrives in Italy, bringing elephants to back up his army.

280/9 The Samnites join Pyrrhus.

280/10 Pyrrhus offers to negotiate with the Romans.

280/13 Pyrrhus defeats the Romans at the battle of Heraclea.

280/28 Pyrrhus advances on Rome, as far as Anagnia in Latium.

280/29 Pyrrhus retires to Campania.

280/31 Rome as the ambassador of Pyrrhus, and unsuccessfully attempts to

280/32 The senate rejects Pyrrhus' peace terms, after a speech by Ap.Claudiu

280/33 Cineas returns to Pyrrhus, and calls the Roman senate "a parliament

280/34 Fabricius is sent on a mission to Pyrrhus.

280/35 Pyrrhus releases the Roman prisoners.

The inscription (Sylloge, 392) on a bronze tablet that was dedicated to Zeus at his sanctuary at Dodona (Epirus) after  Pyrrhus’ victory at Heraclea has been translated as:

1. “King Pyrrhos, the Epirotes and the Tarentines dedicate these spoils from the Romans and their allies to Zeus Naïos”
   

279 BC

279/24 Pyrrhus invades Apulia, and is confronted by the Roman army.

279/25 Pyrrhus defeats the Romans at Asculum, but suffers heavy losses.

Roman treaty with the Carthaginians (Polybius: ‘Histories’, 3: 25: 1-5)

Pyrrhus in Sicily (278-6 BC) 

Final Phase of the war (276 - 275 BC)

276/20 Pyrrhus leaves Sicily and returns to Italy; he is attacked and defeat

275/3 Curius enlists an army to fight against Pyrrhus.

275/11 Pyrrhus sacks the town of Locri, together with the temple of Persepho

275/12 Pyrrhus' fleet is caught in a storm after leaving Locri.

275/14 Pyrrhus asks Antigonus for aid to continue the war in Italy.

275/15 Hieron makes an alliance with Pyrrhus.

275/16 Pyrrhus attempts to raise recruits in Samnium.

275/17 The Romans defeat Pyrrhus at the battle of Beneventum.

275/18 Pyrrhus punishes some of the Tarentines for treachery.

275/21 Pyrrhus considers building a causeway over the sea from Apollonia to

275/22 General comments on the war between Rome and Pyrrhus.

275/23 Pyrrhus leaves Italy; the end of the war between Rome and Pyrrhus.

274/1 The triumph of Curius, over Pyrrhus and the Samnites.