Map by Wikipedia User: Andrew c, CC BY 3.0, https://commons.wikimedia.org/w/index.php?curid=743768
The Babylonians destroyed Jerusalem and the First Temple in ca. 587 BCE. The people of Judah were then exiled to Babylon.
It is to be noted that there were Edomites in Idumea (Edom) and ALSO in other areas. These included in part of the Phoenician city of Tyre, among the Babylonians themselves, in Italy among the founders of Rome, in Germany, and elsewhere.
The Edomites had formerly lived in Edom to the south and southeast of Judah including Petra but they were forced out by the Nabatean Arabs with whom however they also inter-mixed. This could be why "The Rock" (Petra) is associated with Edom in the Bible (e.g. Obadiah 1:3, Jeremiah 49:15-16).
After the Jews were exiled Edomites from the south advanced northward occupying areas evacuated by the Exile Jews. Edomites reached as far north as Maresha and Hebron.
2. Edom and Judah in Roman Times
The Edomites had practised circumcision in the past but due to Helenistic (Greek) influence certain northern Edomite cities (Adoram and Maresha) bordering Judah had ceased to do. These areas were conquered by the Hasmonean (Maccabee) monarch Judah ha_Maccabee and after him again by John Hycrcanus (Hyrcanus-2) of Judah (reigned 134-104 BCE). He allowed the Edomites to stay on condition that they accept circumcision and live by the other Jewish laws. "In truth, out of love for their homeland they accepted circumcision with the other Jewish customs and were henceforth likewise Jewish."
There were however Edomites who kept their old religion without leaving. They worshipped the pagan god Kos which is also the name given in Germany to the god "Woden." Part of the Germans, like the Romans, were of Edomite descent.
In 63 BCE the Roman general Pompey took control of Judaea. Pompey was followed by Julius Caesar who appointed an Edomite (Idumaean) named Antipater as Procurator i.e. Governor on behalf of Rome. The son of Antipater known as Herod the Great was declared King of Judaea by the Roman Senate in 40 BCE.
The brother-in law of Herod was an Edomite named "Costobar." The name is constructed with that of Cos, the chief Edomite god. He was descended from priests of Cos, and hoped to lead his fellow Idumeans to independence from the Jews and Jewish customs. Nevertheless many Idumeans served on the side of Jews in the revolt against Rome (66-70 CE).
Herod the great died in 4 BCE and the Kingdom was divided into "tetrachies" (i.e. third parts) among three of his sons:
1. Judaea i.e. historic Judea, plus Samaria and Idumea. This was ruled by Archelaus who was dismissed in 6 CE by the Roman emperor Augustus.
2. Herod Antipas, ruled as tetrarch of Galilee and Perea (east of the Jordan) from 4 BCE to 39 CE, being then dismissed by the Emperor Caligula.
3. Philip, ruled over the northeastern part.
Herod Agrippa-1 was made King of the Jews over ruled over most of the former domain of Herod the Great from 41-44 CE. He was another descendant of Herod the Great. He lived as a Religious Jew and interceded on behalfÂ of the Jews in Egypt.
When Agrippa died in 4 BCE the province was ruled by Roman Procurators who oppressed the Jews.
In 66 CE Judaea rebelled against Rome. Roman forces were sent to suppress the revolt. During 66, a Judean Free Government was formed in Jerusalem. Its leaders were the former High Priest Ananus ben Ananus, Joseph ben Gurion and Joshua ben Gamla. Yosef ben Matityahu (i.e. Jopsephus) was appointed the rebel commander in Galilee and Eleazar ben Hanania as the commander in Edom.
Nero was the Emperor of Rome at the time. The Romans were also in part descended from Edomites.
The Roman Commander, Vespasian, and his son Titus conquered the Galilee. The Rebellious Jews were divided into different political and perhaps religious parties. The Zealots were the most fanatical and uncompromising. After the defeat in Galilee the Zealots fled to Jerusalem.
Jerusalem previously had been dominated at that time by the Sadducees. These were opposed by the Zealots and conflict broke out in 68 CE. Ananus, the former High Priest, incited the people to rise up against the Zealots who were in control of the Temple. The Zealots believed that Ananus had intentions to betray the city to Rome. The Zealots asked the Idumeans for assistance. When the Edomites arrived, the Zealots opened the gates of Jerusalem to them, and the Edomites slaughtered ben Hanan's (Ananus ben Ananus) forces, killing him as well. Josephus says that 20,000 Idumeans came to assist the Zealots. The Edomites and Zealots then began to massacre the common people of Jerusalem. After that most of the Edomites returned to Idumea but some remained. Jerusalem mostly remained in the control of the Zealots until 70 CE, when it was sacked by Rome and the Temple was destroyed.
Simon bar Giora had been one of the Rebel commanders against Rome. He was opposed to the Judean Free Government and Ananus. When Ananus was killed Simon attacked the Idumeans of Upper Idumea destroying most of the region. Why he did that is not certain. Eventually Simon was forced by Roman pressure to take refuge in Jerusalem where he stayed until being taken prisoner in its capture.
Zealot Temple Siege
The Edomites by Stephen Langfur. The conversion of the Edomites (Idumeans)
Josephus, The Wars of the Jews.