Decapolis (Greek: Δεκάπολις): a union of ten towns. The best known Decapolis was in what is now Jordan.
In c.333 BCE, the Macedonian conqueror Alexander the Great defeated his opponent Darius III Codomannus at Issus. The main consequence of his victory was that all land west of the river Euphrates, already part of a gradually intensifying trade network surrounding the eastern Mediterranean, become increasingly exposed to Greek civilization. However, Hellenism could also meet with resistance. The Maccabaean Revolt in Judaea is the best-known example, although it did not prevent the rise of two Hellenistic dynasties (the Hasmonaeans and the Herodians). The Nabataean Arabs, who lived in the south of modern Jordan, were more efficient. In c.312 BCE, they managed to survive two attacks by Greek armies, and in 64-62, when the Roman general Pompey the Great reorganized the Near East, they managed to stay outside the Roman system: recognized as allies, they retained some independence.
Yet, west of the Euphrates, the spread of Hellenism was an irreversible process, and the most remarkable form of expression was urbanism. The descendants of Alexander's generals, the Ptolemies and the Seleucids, founded many cities.
When Pompey reorganized the Near East and made an end to the Seleucid Empire, he also awarded some kind of independence to a group of Hellenized cities, which was called the Decapolis. They were not as independent as the Nabataeans, but were not a province either, although they had to deal with an official, a prefect, who was responsible to the governor of Syria. The date on the coins of these towns was based on an era that started in 64/63, but in other aspects, they had almost nothing in common: the Decapolis appears not to have been a league of cities with institutions of its own. Urban autonomy was left intact, and the non-demanding nature of its membership can also be deduced from the fact that the number of members varied.
Writing in c. 75 CE, Pliny the Elder offers a list of precisely ten member cities. He visited the land during the Jewish Revolt (66-70), so he knows what he's talking about.
Next to Judaea is the Decapolis, which is so named after the number of its cities, but not all authorities agree about their names. Most writers, however, agree that Damascus is one of the ten. This town is on the banks of the river Chrysorroös, which is eagerly used to irrigate its meadows; the cities of Philadelphia and Rhaphana are in the direction of Arabia; Scythopolis - which Father Liber (Dionysus) used to call Nysa, after he had buried his nurse on this place - owes, its present name from a Scythian colony that was once established there; Gadara, on the banks of the river Hieromix; Hippo; Dion; Pella, rich with its waters; and finally Galasa and Canatha.note[Pliny the Elder, Natural History 5.74.]
"Galasa" is better known as Gerasa. Other cities that have been reckoned among the Decapolis are Abila and Capitolias. Writing a century later, Ptolemy names no less than eighteen cities.note[Ptolemy, Geography 5.14-22.]
Most of these cities were new foundations, others were ancient towns with new names. For example, the capital of the Ammonites was renamed Philadelphia, and although there were many new monuments, it retained older characteristics. Yet, whatever their origins, the cities shared an important sentimental tie: they were Greek towns, not Jewish or Nabataean. During the Jewish War, they were loyal supporters of Rome. Their Greekness was shown with elaborate foundation myths, like Scythopolis' claim to have been founded by Dionysus. This Greekness, on the other hand, did not exclude the possibility of religious syncretism. Ancient Semitic deities could survive under new names; for instance, YHVH could be renamed Dionysus or Zeus - much to the horror of pious Jews of course.
If there had been any political significance to the lose confederation, it was finally abandoned in 106 CE, when the Roman emperor Trajan annexed Nabataea. The provinces were reorganized, and the towns of the Decapolis were divided: some became part of Judaea, others of Nabataea, still others were added to Syria. Yet, there may have remained shared cultural activities, sentiments, and ties, and the name did not immediately vanish, as we can deduce from the use of the word "Decapolis" by Ptolemy.