Hellenistic Period

The word originated from Ancient Greek Ἑλληνιστής (Hellēnistḗs, "one who uses the Greek language"), from Ἑλλάς (Hellás, "Greece"); as if "Hellenist" + "ic".

The idea of a Hellenistic period has been attributed to the 19th-century German historian Johann Gustav Droysen, who in his classic work Geschichte des Hellenismus (History of Hellenism), coined the term Hellenistic to refer to and define the period when Greek culture spread in the non-Greek world after Alexander's conquest. Following this, Hellenistic and related terms, e.g. Hellenism, have been widely used in various contexts. Words related in form or meaning, e.g. Hellenist (Ancient Greek: Ἑλληνιστής, Hellēnistēs), have been attested since ancient times.

Ancient Greece was a patchwork of independent city-states and kingdoms. After the Peloponnesian War (431-404 BC), Sparta held a hegemony that was later displaced by Thebes following the Battle of Leuctra (371 BC). The indecisive outcome at the Battle of Mantinea (362 BC) left the Greek world fragmented, creating conditions in which the northern Greek kingdom of Macedon rose to predominance under king Philip II. Macedon lay on the geographical periphery of the Greek world. Some contemporaries in the southern poleis disparaged it as less urbanised, although the royal Argead dynasty traced Greek descent. The kingdom controlled a large territory and possessed a comparatively strong centralised monarchy, unlike most poleis.

Philip II pursued expansion wherever opportunity allowed. In 352 BC he annexed Thessaly and Magnesia. In 338 BC he defeated a combined Theban and Athenian army at the Battle of Chaeronea after a decade of intermittent conflict. In the aftermath Philip formed the League of Corinth, bringing most of Greece under his leadership. He was elected Hegemon of the League, and a campaign against the Achaemenid Empire was planned. In 336 BC, while preparations were under way, he was assassinated.

Succeeding his father, Alexander took command of the Persian war. Over a decade of campaigning he overthrew the Achaemenid Empire and the king Darius III. The conquered lands included Asia Minor, Assyria, the Levant, Egypt, Mesopotamia, Media, Persia, and parts of modern Afghanistan, Pakistan, and the central Asian steppes. The strain of continuous campaigning was severe, and Alexander died in 323 BC.

After his death, the territories he had conquered experienced sustained Greek cultural influence (Hellenisation) for the next two or three centuries, until the rise of the Roman Empire in the west and the Parthian Empire in the east. As Greek and Levantine cultures interacted, a hybrid Hellenistic culture developed and persisted even when far from the principal Greek centres, for example in the Greco-Bactrian kingdom.

Scholars note that not all changes across the former empire can be attributed solely to Greek rule. As Peter Green observes, diverse phenomena of conquest are often grouped under the term Hellenistic period. In several regions, including Egypt and parts of Asia Minor and Mesopotamia, Alexander was sometimes received as a liberator rather than as a mere conqueror.

In the subsequent era, much of the area continued under the Diadochi, Alexander’s generals and successors. The empire was initially divided among them, though some territories were quickly lost or only nominally acknowledged Macedonian authority. After about two centuries, the remaining successor states were much reduced, culminating in the Roman conquest of Ptolemaic Egypt.

When Alexander the Great died (10 June 323 BC), he left behind a sprawling empire that was composed of many essentially autonomous territories called satrapies. Without a chosen successor, there were immediate disputes among his generals as to who should be king of Macedon. These generals became known as the Diadochi (Ancient Greek: Διάδοχοι, Diadokhoi, meaning "Successors").

Meleager and the infantry supported the candidacy of Alexander's half-brother, Philip Arrhidaeus, while Perdiccas, the leading cavalry commander, supported waiting until the birth of Alexander's child by Roxana. After the infantry stormed the palace of Babylon, a compromise was arranged – Arrhidaeus (as Philip III) should become king and should rule jointly with Roxana's child, assuming that it was a boy (as it was, becoming Alexander IV). Perdiccas himself would become regent (epimeletes) of the empire, and Meleager his lieutenant. Soon, however, Perdiccas had Meleager and the other infantry leaders murdered and assumed full control. The generals who had supported Perdiccas were rewarded in the partition of Babylon by becoming satraps of the various parts of the empire, but Perdiccas' position was shaky because, as Arrian writes, "everyone was suspicious of him, and he of them".

The first of the Diadochi wars broke out when Perdiccas planned to marry Alexander's sister Cleopatra and began to question Antigonus I Monophthalmus' leadership in Asia Minor. Antigonus fled for Greece, and then, together with Antipater and Craterus (the satrap of Cilicia who had been in Greece fighting the Lamian war) invaded Anatolia. The rebels were supported by Lysimachus, the satrap of Thrace and Ptolemy, the satrap of Egypt. Although Eumenes, satrap of Cappadocia, defeated the rebels in Asia Minor, Perdiccas himself was murdered by his own generals Peithon, Seleucus, and Antigenes (possibly with Ptolemy's aid) during his invasion of Egypt (c. 21 May to 19 June, 320 BC). Ptolemy came to terms with Perdiccas's murderers, making Peithon and Arrhidaeus regents in his place, but soon these came to a new agreement with Antipater at the Treaty of Triparadisus. Antipater was made regent of the Empire, and the two kings were moved to Macedon. Antigonus remained in charge of Asia Minor, Ptolemy retained Egypt, Lysimachus retained Thrace and Seleucus I controlled Babylon.

The second Diadochi war began following the death of Antipater in 319 BC. Passing over his own son, Cassander, Antipater had declared Polyperchon his successor as Regent. Cassander rose in revolt against Polyperchon (who was joined by Eumenes) and was supported by Antigonus, Lysimachus and Ptolemy. In 317 BC, Cassander invaded Macedonia, attaining control of Macedon, sentencing Olympias to death and capturing the boy king Alexander IV, and his mother. In Asia, Eumenes was betrayed by his own men after years of campaign and was given up to Antigonus who had him executed.

The third war of the Diadochi broke out because of the growing power and ambition of Antigonus. He began removing and appointing satraps as if he were king and also raided the royal treasuries in Ecbatana, Persepolis and Susa, making off with 25,000 talents. Seleucus was forced to flee to Egypt and Antigonus was soon at war with Ptolemy, Lysimachus, and Cassander. He then invaded Phoenicia, laid siege to Tyre, stormed Gaza and began building a fleet. Ptolemy invaded Syria and defeated Antigonus' son, Demetrius Poliorcetes, in the Battle of Gaza of 312 BC which allowed Seleucus to secure control of Babylonia, and the eastern satrapies. In 310 BC, Cassander had young King Alexander IV and his mother Roxana murdered, ending the Argead dynasty which had ruled Macedon for several centuries.

Antigonus then sent his son Demetrius to regain control of Greece. In 307 BC he took Athens, expelling Demetrius of Phaleron, Cassander's governor, and proclaiming the city free again. Demetrius now turned his attention to Ptolemy, defeating his fleet at the Battle of Salamis and taking control of Cyprus. In the aftermath of this victory, Antigonus took the title of king (basileus) and bestowed it on his son Demetrius Poliorcetes, the rest of the Diadochi soon followed suit. Demetrius continued his campaigns by laying siege to Rhodes and conquering most of Greece in 302 BC, creating a league against Cassander's Macedon.

The decisive engagement of the war came when Lysimachus invaded and overran much of western Anatolia, but was soon isolated by Antigonus and Demetrius near Ipsus in Phrygia. Seleucus arrived in time to save Lysimachus and utterly crushed Antigonus at the Battle of Ipsus in 301 BC. Seleucus' war elephants proved decisive; Antigonus was killed, and Demetrius fled back to Greece to attempt to preserve the remnants of his rule, thereby recapturing a rebellious Athens. Meanwhile, Lysimachus took over Ionia, Seleucus took Cilicia, and Ptolemy captured Cyprus.

After Cassander's death in c. 298 BC, however, Demetrius, who still maintained a sizable loyal army and fleet, invaded Macedon, seized the Macedonian throne (294 BC) and conquered Thessaly and most of central Greece (293–291 BC). He was defeated in 288 BC when Lysimachus of Thrace and Pyrrhus of Epirus invaded Macedon on two fronts, and quickly carved up the kingdom for themselves. Demetrius fled to central Greece with his mercenaries and began to build support there and in the northern Peloponnese. He once again laid siege to Athens after they turned on him, but then struck a treaty with the Athenians and Ptolemy, which allowed him to cross over to Asia Minor and wage war on Lysimachus' holdings in Ionia, leaving his son Antigonus Gonatas in Greece. After initial successes, he was forced to surrender to Seleucus in 285 BC and later died in captivity. Lysimachus, who had seized Macedon and Thessaly for himself, was forced into war when Seleucus invaded his territories in Asia Minor and was defeated and killed in 281 BC at the Battle of Corupedium, near Sardis. Seleucus then attempted to conquer Lysimachus' European territories in Thrace and Macedon, but he was assassinated by Ptolemy Ceraunus ("the thunderbolt"), who had taken refuge at the Seleucid court and then had himself acclaimed as king of Macedon. Ptolemy was killed when Macedon was invaded by Gauls in 279 BC—his head stuck on a spear—and the country fell into anarchy. Antigonus II Gonatas invaded Thrace in the summer of 277 and defeated a large force of 18,000 Gauls. He was quickly hailed as king of Macedon and went on to rule for 35 years.

At this point the tripartite territorial division of the Hellenistic age was in place, with the main Hellenistic powers being Macedon under Demetrius's son Antigonus II Gonatas, the Ptolemaic kingdom under Ptolemy's son Ptolemy II and the Seleucid empire under Seleucus' son Antiochus I Soter.

Epirus was a northwestern Greek kingdom in the western Balkans ruled by the Molossian Aeacidae dynasty. Epirus was an ally of Macedon during the reigns of Philip II and Alexander.

In 281 Pyrrhus (nicknamed "the eagle", aetos) invaded southern Italy to aid the city state of Tarentum. Pyrrhus defeated the Romans in the Battle of Heraclea and at the Battle of Asculum. Though victorious, he was forced to retreat due to heavy losses, hence the term "Pyrrhic victory". Pyrrhus then turned south and invaded Sicily but was unsuccessful and returned to Italy. After the Battle of Beneventum (275 BC) Pyrrhus lost all his Italian holdings and left for Epirus.

Pyrrhus then went to war with Macedonia in 275 BC, deposing Antigonus II Gonatas and briefly ruling over Macedonia and Thessaly until 272. Afterwards, he invaded southern Greece and was killed in battle against Argos in 272 BC. After the death of Pyrrhus, Epirus remained a minor power. In 233 BC the Aeacid royal family was deposed and a federal state was set up called the Epirote League. The league was conquered by Rome in the Third Macedonian War (171–168 BC).

Antigonus II, a student of Zeno of Citium, spent most of his rule defending Macedon against Epirus and cementing Macedonian power in Greece, first against the Athenians in the Chremonidean War, and then against the Achaean League of Aratus of Sicyon. Under the Antigonids, Macedonia was often short on funds, the Pangaeum mines were no longer as productive as under Philip II, the wealth from Alexander's campaigns had been used up and the countryside pillaged by the Gallic invasion. A large number of the Macedonian population had also been resettled abroad by Alexander or had chosen to emigrate to the new eastern Greek cities. Up to two-thirds of the population emigrated, and the Macedonian army could only count on a levy of 25,000 men, a significantly smaller force than under Philip II.

Antigonus II ruled until his death in 239 BC. His son Demetrius II soon died in 229 BC, leaving a child (Philip V) as king, with the general Antigonus Doson as regent. Doson led Macedon to victory in the war against the Spartan king Cleomenes III, and occupied Sparta.

Philip V, who came to power when Doson died in 221 BC, was the last Macedonian ruler with both the talent and the opportunity to unite Greece and preserve its independence against the "cloud rising in the west": the ever-increasing power of Rome. He was known as "the darling of Hellas". Under his auspices the Peace of Naupactus (217 BC) brought the latest war between Macedon and the Greek leagues (the Social War of 220–217 BC) to an end, and at this time he controlled all of Greece except Athens, Rhodes and Pergamum.

In 215 BC Philip, with his eye on Illyria, formed an alliance with Rome's enemy Hannibal of Carthage, which led to Roman alliances with the Achaean League, Rhodes and Pergamum. The First Macedonian War broke out in 212 BC, and ended inconclusively in 205 BC. Philip continued to wage war against Pergamum and Rhodes for control of the Aegean (204–200 BC) and ignored Roman demands for non-intervention in Greece by invading Attica. In 198 BC, during the Second Macedonian War Philip was decisively defeated at Cynoscephalae by the Roman proconsul Titus Quinctius Flamininus and Macedon lost all its territories in Greece proper. Southern Greece was now thoroughly brought into the Roman sphere of influence, though it retained nominal autonomy. The end of Antigonid Macedon came when Philip V's son, Perseus, was defeated and captured by the Romans in the Third Macedonian War (171–168 BC).

During the Hellenistic period, the importance of Greece proper within the Greek-speaking world declined sharply. The great centers of Hellenistic culture were Alexandria and Antioch, capitals of Ptolemaic Egypt and Seleucid Syria respectively. The conquests of Alexander greatly widened the horizons of the Greek world, making the endless conflicts between the cities that had marked the 5th and 4th centuries BC seem petty and unimportant. It led to a steady emigration, particularly of the young and ambitious, to the new Greek empires in the east. Many Greeks migrated to Alexandria, Antioch, and the many other new Hellenistic cities founded in Alexander's wake, as far away as modern Afghanistan and Pakistan.

Independent city states were unable to compete with Hellenistic kingdoms and were usually forced to ally themselves to one of them for defense, giving honors to Hellenistic rulers in return for protection. One example is Athens, which had been decisively defeated by Antipater in the Lamian war (323–322 BC) and had its port in the Piraeus garrisoned by Macedonian troops who supported a conservative oligarchy. After Demetrius Poliorcetes captured Athens in 307 BC and restored the democracy, the Athenians honored him and his father Antigonus by placing gold statues of them on the agora and granting them the title of king. Athens later allied itself to Ptolemaic Egypt to throw off Macedonian rule, eventually setting up a religious cult for the Ptolemaic kings and naming one of the city's phyles in honour of Ptolemy for his aid against Macedon. In spite of the Ptolemaic monies and fleets backing their endeavors, Athens and Sparta were defeated by Antigonus II during the Chremonidean War (267–261 BC). Athens was then occupied by Macedonian troops, and run by Macedonian officials.

Sparta remained independent, but it was no longer the leading military power in the Peloponnese. The Spartan king Cleomenes III (235–222 BC) staged a military coup against the conservative ephors and pushed through radical social and land reforms in order to increase the size of the shrinking Spartan citizenry able to provide military service and restore Spartan power. Sparta's bid for supremacy was crushed at the Battle of Sellasia (222 BC) by the Achaean league and Macedon, who restored the power of the ephors.

Other city states formed federated states in self-defense, such as the Aetolian League (est. 370 BC), the Achaean League (est. 280 BC), the Boeotian league, the "Northern League" (Byzantium, Chalcedon, Heraclea Pontica and Tium) and the "Nesiotic League" of the Cyclades. These federations involved a central government which controlled foreign policy and military affairs, while leaving most of the local governing to the city states, a system termed sympoliteia. In states such as the Achaean league, this also involved the admission of other ethnic groups into the federation with equal rights, in this case, non-Achaeans. The Achean league was able to drive out the Macedonians from the Peloponnese and free Corinth, which duly joined the league.

One of the few city states who managed to maintain full independence from the control of any Hellenistic kingdom was Rhodes. With a skilled navy to protect its trade fleets from pirates and an ideal strategic position covering the routes from the east into the Aegean, Rhodes prospered during the Hellenistic period. It became a center of culture and commerce, its coins were widely circulated and its philosophical schools became one of the best in the Mediterranean. After holding out for one year under siege by Demetrius Poliorcetes (305–304 BC), the Rhodians built the Colossus of Rhodes to commemorate their victory. They retained their independence by the maintenance of a powerful navy, by maintaining a carefully neutral posture and acting to preserve the balance of power between the major Hellenistic kingdoms.

Initially, Rhodes had very close ties with the Ptolemaic kingdom. Rhodes later became a Roman ally against the Seleucids, receiving some territory in Caria for their role in the Roman–Seleucid War (192–188 BC).

The west Balkan coast was inhabited by various Illyrian tribes and kingdoms such as the kingdom of the Dalmatae and of the Ardiaei, who often engaged in piracy under Queen Teuta (reigned 231–227 BC). Further inland was the Illyrian Paeonian Kingdom and the tribe of the Agrianes. Illyrians on the coast of the Adriatic were under the effects and influence of Hellenisation and some tribes adopted Greek, becoming bilingual due to their proximity to the Greek colonies in Illyria. Illyrians imported weapons and armor from the ancient Greeks (such as the Illyrian type helmet, originally a Greek type) and also adopted the ornamentation of ancient Macedon on their shields and their war belts (a single one has been found, dated 3rd century BC at modern Selcë e Poshtme, a part of Macedon at the time under Philip V of Macedon).

The Odrysian Kingdom was a union of Thracian tribes under the kings of the powerful Odrysian tribe. Various parts of Thrace were under Macedonian rule under Philip II of Macedon, Alexander the Great, Lysimachus, Ptolemy II, and Philip V but were also often ruled by their own kings. The Thracians and Agrianes were widely used by Alexander as peltasts and light cavalry, forming about one-fifth of his army. The Diadochi also used Thracian mercenaries in their armies and they were also used as colonists. The Odrysians used Greek as the language of administration and of the nobility. The nobility also adopted Greek fashions in dress, ornament, and military equipment, spreading it to the other tribes. Thracian kings were among the first to be Hellenized.

After 278 BC the Odrysians had a strong competitor in the Celtic Kingdom of Tylis ruled by the kings Comontorius and Cavarus, but in 212 BC they conquered their enemies and destroyed their capital.

Southern Italy (Magna Graecia) and south-eastern Sicily had been colonized by the Greeks during the 8th century BC. In 4th-century BC Sicily the leading Greek city and hegemon was Syracuse. During the Hellenistic period the leading figure in Sicily was Agathocles of Syracuse (361–289 BC) who seized the city with an army of mercenaries in 317 BC. Agathocles extended his power throughout most of the Greek cities in Sicily, fought a long war with the Carthaginians, at one point invading Tunisia in 310 BC and defeating a Carthaginian army there. This was the first time a European force had invaded the region. After this war he controlled most of south-east Sicily and had himself proclaimed king, in imitation of the Hellenistic monarchs of the east. Agathocles then invaded Italy (c. 300 BC) in defense of Tarentum against the Bruttians and Romans, but was unsuccessful.

Greeks in pre-Roman Gaul were mostly limited to the Mediterranean coast of Provence, France. The first Greek colony in the region was Massalia, which became one of the largest trading ports of Mediterranean by the 4th century BC with 6,000 inhabitants. Massalia was also the local hegemon, controlling various coastal Greek cities like Nice and Agde. The coins minted in Massalia have been found in all parts of Liguro-Celtic Gaul. Celtic coinage was influenced by Greek designs, and Greek letters can be found on various Celtic coins, especially those of Southern France. Traders from Massalia ventured inland deep into France on the Rivers Durance and Rhône, and established overland trade routes deep into Gaul, and to Switzerland and Burgundy. The Hellenistic period saw the Greek alphabet spread into southern Gaul from Massalia (3rd and 2nd centuries BC) and according to Strabo, Massalia was also a center of education, where Celts went to learn Greek. A staunch ally of Rome, Massalia retained its independence until it sided with Pompey in 49 BC and was then taken by Caesar's forces.

The city of Emporion (modern Empúries), originally founded by Archaic-period settlers from Phocaea and Massalia in the 6th century BC near the village of Sant Martí d'Empúries (located on an offshore island that forms part of L'Escala, Catalonia, Spain), was reestablished in the 5th century BC with a new city (neapolis) on the Iberian mainland.

The Hellenistic states of Asia and Egypt were run by an occupying imperial elite of Greco-Macedonian administrators and governors propped up by a standing army of mercenaries and a small core of Greco-Macedonian settlers. Promotion of immigration from Greece was important in the establishment of this system. Hellenistic monarchs ran their kingdoms as royal estates and most of the heavy tax revenues went into the military and paramilitary forces which preserved their rule from any kind of revolution. Macedonian and Hellenistic monarchs were expected to lead their armies on the field, along with a group of privileged aristocratic companions or friends (hetairoi, philoi) which dined and drank with the king and acted as his advisory council. The monarch was also expected to serve as a charitable patron of the people; this public philanthropy could mean building projects and handing out gifts but also promotion of Greek culture and religion.

Ptolemy, a somatophylax, one of the seven bodyguards who served as Alexander the Great's generals and deputies, was appointed satrap of Egypt after Alexander's death in 323 BC. In 305 BC, he declared himself King Ptolemy I, later known as "Soter" (saviour) for his role in helping the Rhodians during the siege of Rhodes. Ptolemy built new cities such as Ptolemais Hermiou in upper Egypt and settled his veterans throughout the country, especially in the region of the Faiyum. Alexandria, a major center of Greek culture and trade, became his capital city. As Egypt's first port city, it became the main grain exporter in the Mediterranean.

The Egyptians begrudgingly accepted the Ptolemies as the successors to the pharaohs of independent Egypt, though the kingdom went through several native revolts. Ptolemy I began to order monetary contributions from the people and, as a result, rewarded cities with high contributions with royal benefaction. This often resulted in the formation of a royal cult within the city. Reservations about this activity slowly dissipated as this worship of mortals was justified by the precedent of the worshipping of Greek heroes. The Ptolemies took on the traditions of the Egyptian Pharaohs, such as marrying their siblings (Ptolemy II was the first to adopt this custom), having themselves portrayed on public monuments in Egyptian style and dress, and participating in Egyptian religious life. The Ptolemaic ruler cult portrayed the Ptolemies as gods, and temples to the Ptolemies were erected throughout the kingdom. Ptolemy I even created a new god, Serapis, who was a combination of two Egyptian gods: Apis and Osiris, with attributes of Greek gods. Ptolemaic administration was, like the ancient Egyptian bureaucracy, highly centralized and focused on squeezing as much revenue out of the population as possible through tariffs, excise duties, fines, taxes, and so forth. A whole class of petty officials, tax farmers, clerks, and overseers made this possible. The Egyptian countryside was directly administered by this royal bureaucracy. External possessions such as Cyprus and Cyrene were run by strategoi, military commanders appointed by the crown.

Under Ptolemy II, Callimachus, Apollonius of Rhodes, Theocritus, and a host of other poets including the Alexandrian Pleiad made the city a center of Hellenistic literature. Ptolemy himself was eager to patronise the library, scientific research and individual scholars who lived on the grounds of the library. He and his successors also fought a series of wars with the Seleucids, known as the Syrian wars, over the region of Coele-Syria. Ptolemy IV won the great battle of Raphia (217 BC) against the Seleucids, using native Egyptians trained as phalangites. However these Egyptian soldiers revolted, eventually setting up a native breakaway Egyptian state in the Thebaid between 205 and 186/185 BC, severely weakening the Ptolemaic state.

Ptolemy's family ruled Egypt until the Roman conquest of 30 BC. All the male rulers of the dynasty took the name Ptolemy. Ptolemaic queens, some of whom were the sisters of their husbands, were usually called Cleopatra, Arsinoe, or Berenice. The most famous member of the line was the last queen, Cleopatra VII, known for her role in the Roman political battles between Julius Caesar and Pompey, and later between Octavian and Mark Antony. Her suicide at the conquest by Rome marked the end of Ptolemaic rule in Egypt, though Hellenistic culture continued to thrive in Egypt throughout the Roman and Byzantine periods until the Muslim conquest.

Following division of Alexander's empire, Seleucus I Nicator received Babylonia. From there, he created a new empire which expanded to include much of Alexander's Near Eastern territories. At the height of its power, it included central Anatolia, the Levant, Mesopotamia, Persia, today's Turkmenistan, Pamir, and parts of Pakistan. It included a diverse population estimated at fifty to sixty million people.

Under Antiochus I (c. 324/323 – 261 BC), however, the unwieldy empire was already beginning to shed territories. Pergamum broke away under Eumenes I who defeated a Seleucid army sent against him. The kingdoms of Cappadocia, Bithynia and Pontus were all practically independent by this time as well. Like the Ptolemies, Antiochus I established a dynastic religious cult, deifying his father Seleucus I. Seleucus, officially said to be descended from Apollo, had his own priests and monthly sacrifices. The erosion of the empire continued under Seleucus II, who was forced to fight a civil war (239–236 BC) against his brother Antiochus Hierax and was unable to keep Bactria, Sogdiana and Parthia from breaking away. Hierax carved off most of Seleucid Anatolia for himself, but was defeated, along with his Galatian allies, by Attalus I of Pergamon who now also claimed kingship.

The vast Seleucid Empire was, like Egypt, mostly dominated by a Greco-Macedonian political elite. The Greek population of the cities who formed the dominant elite were reinforced by emigration from Greece. These cities included newly founded colonies such as Antioch, the other cities of the Syrian tetrapolis, Seleucia (north of Babylon) and Dura-Europos on the Euphrates. These cities retained traditional Greek city state institutions such as assemblies, councils and elected magistrates, but this was a facade for they were always controlled by the royal Seleucid officials. Apart from these cities, there were also a large number of Seleucid garrisons (choria), military colonies (katoikiai) and Greek villages (komai) which the Seleucids planted throughout the empire to cement their rule. This 'Greco-Macedonian' population (which also included the sons of settlers who had married local women) could make up a phalanx of 35,000 men (out of a total Seleucid army of 80,000) during the reign of Antiochus III. The rest of the army was made up of native troops.

Antiochus III ("the Great") conducted several vigorous campaigns to retake all the lost provinces of the empire since the death of Seleucus I. After being defeated by Ptolemy IV's forces at Raphia (217 BC), Antiochus III led a long campaign to the east to subdue the far eastern breakaway provinces (212–205 BC) including Bactria, Parthia, Ariana, Sogdiana, Gedrosia and Drangiana. He was successful, bringing back most of these provinces into at least nominal vassalage and receiving tribute from their rulers. After the death of Ptolemy IV (204 BC), Antiochus took advantage of the weakness of Egypt to conquer Coele-Syria in the fifth Syrian war (202–195 BC). He then began expanding his influence into Pergamene territory in Asia and crossed into Europe, fortifying Lysimachia on the Hellespont, but his expansion into Anatolia and Greece was abruptly halted after a decisive defeat at the Battle of Magnesia (190 BC). In the Treaty of Apamea which ended the war, Antiochus lost all of his territories in Anatolia west of the Taurus and was forced to pay a large indemnity of 15,000 talents.

Much of the eastern part of the empire was then conquered by the Parthians under Mithridates I of Parthia in the mid-2nd century BC, yet the Seleucid kings continued to rule a rump state from Syria until the invasion by the Armenian king Tigranes the Great and their ultimate overthrow by the Roman general Pompey.

After the death of Lysimachus, one of his officers, Philetaerus, took control of the city of Pergamum in 282 BC along with Lysimachus' war chest of 9,000 talents and declared himself loyal to Seleucus I while remaining de facto independent. His descendant, Attalus I, defeated the invading Galatians and proclaimed himself an independent king. Attalus I (241–197 BC), was a staunch ally of Rome against Philip V of Macedon during the first and second Macedonian Wars. For his support against the Seleucids in 190 BC, Eumenes II was rewarded with all the former Seleucid domains in Asia Minor. Eumenes II turned Pergamon into a centre of culture and science by establishing the Library of Pergamum which was said to be second only to the Library of Alexandria with 200,000 volumes according to Plutarch. It included a reading room and a collection of paintings. Eumenes II also constructed the Pergamum Altar with friezes depicting the Gigantomachy on the acropolis of the city. Pergamum was also a center of parchment (charta pergamena) production. The Attalids ruled Pergamon until Attalus III bequeathed the Kingdom of Pergamon to the Roman Republic in 133 BC to avoid a likely succession crisis.

The Celts who settled in Galatia came through Thrace under the leadership of Leotarios and Leonnorios c. 270 BC. They were defeated by Antiochus I in the 'battle of the Elephants', but were still able to establish a Celtic territory in central Anatolia. The Galatians were well respected as warriors and were widely used as mercenaries in the armies of the successor states. They continued to attack neighboring kingdoms such as Bithynia and Pergamon, plundering and extracting tribute. This came to an end when they sided with the renegade Seleucid prince Antiochus Hierax who tried to defeat Attalus, the ruler of Pergamon (241–197 BC). Attalus severely defeated the Gauls, forcing them to confine themselves to Galatia. The theme of the Dying Gaul (a famous statue displayed in Pergamon) remained a favorite in Hellenistic art for a generation signifying the victory of the Greeks over a noble enemy. In the early 2nd century BC, the Galatians became allies of Antiochus the Great, the last Seleucid king trying to regain suzerainty over Asia Minor. In 189 BC, Rome sent Gnaeus Manlius Vulso on an expedition against the Galatians. Galatia was henceforth dominated by Rome through regional rulers from 189 BC onward.

After their defeats by Pergamon and Rome the Galatians slowly became Hellenized and they were called "Gallo-Graeci" by the historian Justin as well as Ἑλληνογαλάται (Hellēnogalátai) by Diodorus Siculus in his Bibliotheca historica v.32.5, who wrote that they were "called Helleno-Galatians because of their connection with the Greeks."

The Bithynians were a Thracian people living in northwest Anatolia. After Alexander's conquests the region of Bithynia came under the rule of the native king Bas, who defeated Calas, a general of Alexander the Great, and maintained the independence of Bithynia. His son, Zipoetes I of Bithynia maintained this autonomy against Lysimachus and Seleucus I, and assumed the title of king (basileus) in 297 BC. His son and successor, Nicomedes I, founded Nicomedia, which soon rose to great prosperity, and during his long reign (c. 278 – c. 255 BC), as well as those of his successors, the Kingdom of Bithynia held a considerable place among the minor monarchies of Anatolia. Nicomedes also invited the Celtic Galatians into Anatolia as mercenaries, and they later turned on his son Prusias I, who defeated them in battle.

The Greek kingdom of Bactria began as a breakaway satrapy of the Seleucid empire, which, because of the size of the empire, had significant freedom from central control. Between 255 and 246 BC, the governor of Bactria, Sogdiana and Margiana (most of present-day Afghanistan), one Diodotus, took this process to its logical extreme and declared himself king. Diodotus II, son of Diodotus, was overthrown in about 230 BC by Euthydemus, possibly the satrap of Sogdiana, who then started his own dynasty. In c. 210 BC, the Greco-Bactrian kingdom was invaded by a resurgent Seleucid empire under Antiochus III the Great. While victorious in the field, it seems Antiochus came to realise that there were advantages in the status quo (perhaps sensing that Bactria could not be governed from Syria), and married one of his daughters to Euthydemus's son, thus legitimizing the Greco-Bactrian dynasty. Soon afterwards the Greco-Bactrian kingdom seems to have expanded, possibly taking advantage of the defeat of the Parthian king Arsaces II by Antiochus.

According to Strabo, the Greco-Bactrians seem to have had contacts with Han China through the Silk Road trade routes (Strabo, XI.11.1). There is evidence of technology exchange between Bactria and China around this time in the form of metal alloys such as Copper-nickel, which was then unknown to the West. Indian sources also maintain religious contact between Buddhist monks and the Greeks, and some Greco-Bactrians did convert to Buddhism. Demetrius, son and successor of Euthydemus, invaded north-western India around 180 BC, after the destruction of the Mauryan Empire there; the Mauryans were probably allies of the Bactrians (and Seleucids). The exact justification for the invasion remains unclear, but after 180 BC, the Greeks ruled over parts of northwestern India. This period also marks the beginning of the obfuscation of Greco-Bactrian history. Demetrius possibly died in about 180 BC; numismatic evidence suggests the existence of several other kings shortly thereafter. It is probable that at this point the Greco-Bactrian kingdom split into several semi-independent regions for some years, often warring amongst themselves. King Heliocles was the last Greek to clearly rule Bactria, his power collapsing in the face of central Asian tribal invasions (Scythian and Yuezhi), by about 130 BC. However, Greek urban civilisation seems to have continued in Bactria after the fall of the kingdom, having a hellenising effect on the tribes which had displaced Greek rule. The Kushan Empire which followed continued to use Greek on their coinage and Greeks continued being influential in the empire.

The separation of the Indo-Greek kingdom from the Greco-Bactrian kingdom resulted in an even more isolated position, and thus the details of the Indo-Greek kingdom are even more obscure than for Bactria. Many supposed kings in India are known only because of coins bearing their name. After the death of the Greco-Bactrian king Demetrius, civil wars between Bactrian kings in India allowed Apollodotus I (from c. 180/175 BC) to make himself independent as the first proper Indo-Greek king (who did not rule from Bactria). Large numbers of his coins have been found in India, and he seems to have reigned in Gandhara as well as western Punjab. Apollodotus I was succeeded by or ruled alongside Antimachus II, likely the son of the Bactrian king Antimachus I.

In about 155 or 165 BC, a king named Menander rose to power. Menander was the most successful of the Indo-Greek kings and he seems to have been a great patron of Buddhism. He probably became a Buddhist and is remembered in some Buddhist texts as 'Milinda'. He also expanded the kingdom further east into Punjab, though these conquests were rather ephemeral. After the death of Menander (c. 130 BC), the Kingdom appears to have fragmented, with several 'kings' attested contemporaneously in different regions. This inevitably weakened the Greek position, and territory seems to have been lost progressively. Around 70 BC, the western regions of Arachosia and Paropamisadae were lost to tribal invasions, presumably by those tribes responsible for the end of the Bactrian kingdom. The resulting Indo-Scythian kingdom seems to have gradually pushed the remaining Indo-Greek kingdom towards the east. The Indo-Greek kingdom appears to have lingered on in western Punjab until about AD 10, at which time it was finally ended by the Indo-Scythians. Strato III was the last of the dynasty of Diodotus was the last of the line of Diodotus and independent Hellenistic king to rule at his death in 10 AD.

After conquering the Indo-Greeks, the Kushan Empire took over Greco-Buddhism, the Greek language, Greek script, Greek coinage and artistic styles. Greeks continued being an important part of the cultural world of India for generations. The depictions of the Buddha appear to have been influenced by Greek culture: Buddha representations in the Ghandara period often showed Buddha under the protection of Herakles. Several references in Indian literature praise the knowledge of the Yavanas or the Greeks. The Mahabharata compliments them as "the all-knowing Yavanas" (sarvajñā yavanā); e.g., "The Yavanas, O king, are all-knowing; the Suras are particularly so. The mlecchas are wedded to the creations of their own fancy", such as flying machines that are generally called vimanas. The "Brihat-Samhita" of the mathematician Varahamihira says: "The Greeks, though impure, must be honored since they were trained in sciences and therein, excelled others...".