The partition of Alexander's empire (323-281 BC)
Alexander the Great had conquered the Persian Empire within a short time-frame and died young, leaving an expansive empire of partly Hellenized culture without an adult heir. Therefore his generals (the Diadochi) jostled for supremacy over portions of his empire.
Seleucus, one of his generals, established himself in Babylon in 312 BC, used as the foundation date of the Seleucid Empire. He ruled over not only Babylonia, but the entire enormous eastern part of Alexander's Empire. Following his and Lysimachus' victory over Antigonus Monophthalmus at the Battle of Ipsus in 301 BC, Seleucus took control over eastern Anatolia and northern Syria. In the latter area he founded a new capital at Antioch on the Orontes, a city he named after his father. An alternative capital was established at Seleucia on the Tigris, north of Babylon. Seleucus' empire reached its greatest extent following his defeat of his erstwhile ally, Lysimachus, at Corupedion in 281 BC. Seleucus expanded his control to encompass western Anatolia. He hoped further to take control of Lysimachus' lands in Europe - primarily Thrace and even Macedonia itself, but was assassinated by Ptolemy Ceraunus on landing in Europe. His son and successor, Antiochus I Soter, proved unable to pick up where his father had left off in conquering the European portions of Alexander's empire, but was left, nevertheless, with an enormous realm consisting of nearly all of the Asian portions of the Empire. His competitors were Antigonus II Gonatas in Macedonia and Ptolemy II Philadelphus in Egypt.
The Seleucid empire's geographic span, from the Aegean Sea to Afghanistan, brought together a multitude of races: Greeks, Persians, Medes, Jews, Indians, to mention only some. Its rulers were in the position of having a governing interest to implement a policy of racial unity initiated by Alexander. By 313 BC, Hellenic ideas had begun their almost 250-year expansion into the Near East, Middle East, and Central Asian cultures. It was the empire's governmental framework to rule by establishing hundreds of cities for trade and occupational purposes. Many of the existing cities began -- or were compelled by force -- to adopt Hellenized philosophic thought, religious sentiments, and politics. Synthesizing Hellenic and indigenous cultural, religious, and philosophical ideas met with varying degrees of success -- resulting in times of simultaneous peace and rebellion in various parts of the empire.
An overextended domain
Nevertheless, even before Seleucus' death, the vast eastern domains of the Seleucids were proving difficult to assert control over. Seleucus invaded India (modern Punjab) in 304 BC, but was defeated by Chandragupta Maurya (Sandrokottos), founder of the Maurya empire. It is said that Chandragupta fielded an army of 100,000 men and 9,000 war elephants, and forced Seleucus to cede territories in eastern and southern present-day Afghanistan. The peace was strengthened by an alliance guaranteed by Chandragupta's marriage with Seleucus' daughter. In exchange Chandragupta gave him no less than 500 elephants, an addition to his army that was to play a prominent part in his victory at Ipsus.
Seleucus sent an ambassador named Megasthenes to Chandragupta's court, who repeatedly visited Pataliputra (modern Patna in Bihar state), capital of Chandragupta. Megasthenes wrote detailed descriptions of India and Chandragupta's reign, which have been partly preserved to us through Diodorus Siculus.
Other territories lost before Seleucus' death were Gedrosia in the south-east of the Iranian plateau, and, to the north of this, Arachosia on the west bank of the Indus River. Antiochus I (reigned 281-261 BC) and his son and successor Antiochus II Theos (reigned 261-246 BC) were faced with challenges in the west, including repeated wars with Ptolemy II and a Celtic invasion of Asia Minor -- distracting attention from holding the eastern portions of the Empire together. Towards the end of Antiochus II's reign, the eastern provinces of Bactria and Parthia simultaneously asserted their independence.
Greco-Bactrian secession (250 BC)
Diodotus, governor for the Bactrian territory, asserted independence in 250 BC to form the Greco-Bactrian kingdom. This kingdom was characterized by a rich Hellenistic culture, and was to continue its domination of Bactria until around 125 BC, when it was overrun by the invasion of northern nomads. One of the Greco-Bactrian kings, Demetrius I of Bactria, invaded India around 180 BC to form the Greco-Indian kingdom, lasting until 1 BC.
Parthian secession (250 BC)
A Parthian tribal chief called Arsaces took over the Parthian territory from the Seleucid Empire around 250 BC to form the Arsacid Dynasty -- the starting point of the powerful Parthian Empire.
Eclipse and revival
By the time Antiochus II's son Seleucus II Callinicus came to the throne around 246 BC, the Seleucids seemed to be at a low ebb indeed. Aside from the secessions of Parthia and Bactria, Seleucus II was soon dramatically defeated in the Third Syrian War against Ptolemy III of Egypt, then had to fight a civil war against his own brother Antiochus Hierax. In Asia Minor too, the Seleucid dynasty seemed to be losing control -- Gauls had fully established themselves in Galatia, semi-independent semi-Hellenized kingdoms had sprung up in Bithynia, Pontus and Cappadocia, and the city of Pergamum in the west was asserting its independence under the Attalid Dynasty.
But a revival would begin when Seleucus II's younger son, Antiochus III the Great, took the throne in 223 BC. Although initially unsuccessful in the Fourth Syrian War against Egypt, which led to an embarrassing defeat at the Battle of Raphia (217 BC), Antiochus would prove himself to be the greatest of the Seleucid rulers after Seleucus I himself. Following his defeat at Raphia, he spent the next ten years on his Anabasis through the eastern parts of his domain -- restoring rebellious vassals like Parthia and Bactria to at least nominal obedience, and even emulating Alexander with an expedition into India.
Antiochus and Philip V of Macedon then made a compact to divide the Ptolemaic possessions outside of Egypt, and in the Fifth Syrian War, the Seleucids ousted Ptolemy V from control of Coele-Syria. The Battle of Panium (198 BC) definitively transferred these holdings from the Ptolemies to the Seleucids. Antiochus appeared, at the least, to have restored the Seleucid Kingdom to glory.
The power of Rome and renewed disintegration
But Antiochus' glory was not to last for long. Following his erstwhile ally Philip's defeat at the hands of Rome in 197 BC, Antiochus now saw the opportunity for expansion into Greece. Encouraged by the exiled Carthaginian general Hannibal, and making an alliance with the disgruntled Aetolian League, Antiochus invaded Greece. Unfortunately, this decision led to his downfall: he was defeated by the Romans at Thermopylae (191 BC) and Magnesia (190 BC), and was forced to make peace with the Romans by the embarrassing Treaty of Apamia (188 BC) -- which forced him to abandon all European territories, ceded all of Asia Minor north of the Taurus Mountains to Pergamum, and set a large indemnity to be paid. Antiochus died in 187 BC on another expedition to the east, where he sought to extract money to pay the indemnity.
The reign of his son and successor Seleucus IV Philopator (187-175 BC) was largely spent in attempts to pay the large indemnity, and Seleucus was ultimately assassinated by his minister Heliodorus. Seleucus' younger brother, Antiochus IV Epiphanes, now seized the throne. He attempted to restore Seleucid prestige with a successful war against Egypt; but despite driving the Egyptian army back to Alexandria itself, he was forced to withdraw by the Roman envoy Popilius Laena, who famously drew a circle in the sand around the king and told him he had to decide whether or not to withdraw from Egypt before leaving the circle. Antiochus chose to withdraw.
The latter part of his reign saw the further disintegration of the Empire. The Eastern areas remained nearly uncontrollable, as Parthians began to take over the Persian lands; and Antiochus' aggressive Hellenizing (or de-Judaizing) activities led to armed rebellion in Judaea -- the Maccabee revolt. Efforts to deal with both the Parthians and the Jews proved fruitless, and Antiochus himself died during an expedition against the Parthians in 164 BC.
Civil war and further decay
After the death of Antiochus IV Epiphanes, the Seleucid Empire became increasingly unstable. Frequent civil wars made central authority tenuous at best. Epiphanes' young son, Antiochus V Eupator, was first overthrown by Seleucus IV's son, Demetrius I Soter in 161 BC. Demetrius I attempted to restore Seleucid power in Judea particularly, but was overthrown in 150 BC by Alexander Balas -- an impostor who (with Egyptian backing) claimed to be the son of Epiphanes. Alexander Balas reigned until 145 BC, when he was overthrown by Demetrius I's son, Demetrius II Nicator. Demetrius II proved unable to control the whole of the kingdom, however. While he ruled Babylonia and eastern Syria from Damascus, the remnants of Balas' supporters -- first supporting Balas' son Antiochus VI, then the usurping general Diodotus Tryphon -- held out in Antioch.
Meanwhile, the decay of the Empire's territorial possessions continued apace. By 143 BC, the Jews had fully established their independence. Parthian expansion continued as well. In 139 BC, Demetrius II was defeated in battle by the Parthians and was captured. By this time, the entire Iranian Plateau had been lost to Parthian control. Demetrius Nicator's brother, Antiochus VII, was ultimately able to restore a fleeting unity and vigour to the Seleucid domains, but he too proved unequal to the Parthian threat: he was killed in battle with the Parthians in 129 BC, leading to the final collapse of the Seleucid hold on Babylonia. After the death of Antiochus VII, all effective Seleucid rule collapsed, as multiple claimants contested control of what was left of the Seleucid realm in almost unending civil war.
Collapse of the Seleucid Empire
By 100 BC, the once formidable Seleucid Empire encompassed little more than Antioch and some Syrian cities. Despite the clear collapse of their power, and the decline of their kingdom around them, nobles continued to play kingmakers on a regular basis, with occasional intervention from Ptolemaic Egypt and other outside powers. The Seleucids existed solely because no other nation wished to absorb them -- seeing as they constituted a useful buffer between their other neighbours. In the wars in Anatolia between Mithridates VI of Pontus and Sulla of Rome, the Seleucids were largely left alone by both major combatants.
Mithridates' ambitious son-in-law, Tigranes the Great, king of Armenia, however, saw opportunity for expansion in the constant civil strife to the south. In 83 BC, at the invitation of one of the factions in the interminable civil wars, he invaded Syria, and soon established himself as ruler of Syria, putting Seleucid rule virtually at an end.
Seleucid rule was not entirely at an end, however. Following the Roman general Lucullus' defeat of both Mithridates and Tigranes in 69 BC, a rump Seleucid kingdom was restored under Antiochus XIII. Even now, civil wars could not be prevented, as another Seleucid, Philip II, contested rule with Antiochus. After the Roman conquest of Pontus, the Romans became increasingly alarmed at the constant source of instability in Syria under the Seleucids. Once Mithridates was defeated by Pompey in 63 BC, Pompey set about the task of remaking the Hellenistic East, by creating new client kingdoms and establishing provinces. While client nations like Armenia and Judea were allowed to continue some degree of autonomy under local kings, Pompey saw the Seleucids as too troublesome to continue; and doing away with both rival Seleucid princes, he made Syria into a Roman province.
- Seleucus I Nicator (Satrap 311–305 BC, King 305 BC–281 BC)
- Antiochus I Soter (co-ruler from 291, ruled 281–261 BC)
- Antiochus II Theos (261–246 BC)
- Seleucus II Callinicus ( 246–225 BC)
- Seleucus III Ceraunus (or Soter) ( 225–223 BC)
- Antiochus III the Great (223–187 BC)
- Seleucus IV Philopator (187–175 BC)
- Antiochus IV Epiphanes (175–164 BC)
- Antiochus V Eupator (164–162 BC)
- Demetrius I Soter (161–150 BC)
- Alexander I Balas (154–145 BC)
- Demetrius II Nicator (first reign, 145–138 BC)
- Antiochus VI Dionysus (or Epiphanes) (145–140 BC?)
- Diodotus Tryphon (140?–138 BC)
- Antiochus VII Sidetes (or Euergetes) ( 138–129 BC)
- Demetrius II Nicator (second reign, 129–126 BC)
- Alexander II Zabinas (129–123 BC)
- Cleopatra Thea (126–123 BC)
- Seleucus V Philometor (126/125 BC)
- Antiochus VIII Grypus (125–96 BC)
- Antiochus IX Cyzicenus (114–96 BC)
- Seleucus VI Epiphanes Nicator (96–95 BC)
- Antiochus X Eusebes Philopator (95–92 BC or 83 BC)
- Demetrius III Eucaerus (or Philopator) (95–87 BC)
- Antiochus XI Epiphanes Philadelphus (95–92 BC)
- Philip I Philadelphus (95–84/83 BC)
- Antiochus XII Dionysus (87–84 BC)
- (Tigranes I of Armenia) (83–69 BC)
- Seleucus VII Kybiosaktes or Philometor (70s BC–60s BC?)
- Antiochus XIII Asiaticus (69–64 BC)
- Philip II Philoromaeus (65–63 BC)
- Livius, The Seleucid Empire by Jona Lendering
- Seleukids.org: An Online Sourcebook for the History, Numismatics, Epigraphy, Art and Archaeology of the Seleukid Empire, by Oliver D. Hoover