linguistic:paraphrasing
Collapse (100–63 BC)

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 the Seleucid Empire virtually at an end.

Seleucid rule was not entirely over, 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 so, 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 with some degree of autonomy under local kings, Pompey saw the Seleucids as too troublesome to continue; doing away with both rival Seleucid princes, he made Syria into a Roman province.