The Siege of Jerusalem occurred during Pompey the Great's campaigns in the East, shortly after his successful conclusion of the Third Mithridatic War. Pompey had been asked to intervene in a dispute over inheritance to the throne of the Hasmonean Kingdom, which turned into a war between Hyrcanus II and Aristobulus II. His conquest of Jerusalem, however, spelled the end of Jewish independence and the incorporation of Judea as a client kingdom of the Roman Republic.
Background
The death of Hasmonean queen Alexandra Salome plunged Judea into a civil war between her two sons, Hyrcanus and Aristobulus. After Aristobulus ousted his elder brother from both the throne and the high priesthood in Jerusalem, Antipater the Idumean advised Hyrcanus to enlist the aid of King Aretas III of Nabataea. In return for the promise of territorial concessions, Aretas provided Hyrcanus with 50,000 soldiers, and their joint forces besieged Aristobulus in Jerusalem. Pompey had followed the successful conclusion of the Third Mithridatic War with the creation of the Province of Syria and had spent 64 and 63 BC bringing law and order to the region. Events in Judea prompted Aemilius Scaurus, Pompey's legate in Damascus, to arrive in Jerusalem. Scaurus was approached by both parties, but the issue was settled by a bribe from Aristobulus, and Scaurus ordered Aretas to lift his siege of the city. As the Nabataean army withdrew towards Petra, Aristobulus set off in pursuit and defeated the Nabataeans at Papyron. When Pompey himself arrived in Damascus in 63 BC, both Hyrcanus and Aristobulus visited him there. Pompey put off resolving the issue, informing the opposing parties he would resolve it once he arrived in Judea in person. Aristobulus did not wait for Pompey's decision and left Damascus to shut himself away at his fortress of Alexandrium. This angered Pompey who marched his forces into Judea, at the sight of which Aristobulus yielded. When Aulus Gabinius led a force to take Jerusalem, however, Aristobulus' supporters refused to let the Roman troops in. Incensed, Pompey had Aristobulus arrested and prepared to besiege the city.
Siege
When Pompey arrived in Jerusalem, he surveyed the city: Hyrcanus II still had supporters in the city. They opened a gate, probably in the northwestern part of the city wall, and let the Romans in. This allowed Pompey to take hold of Jerusalem's upper city, including the royal palace, while Aristobulus' party held the eastern portions of the city—the Temple Mount and the City of David. The Jews consolidated their hold by breaking down the bridge over the Tyropoeon Valley connecting the upper city with the Temple Mount. Pompey offered them the chance to surrender, but when they refused, he began prosecuting the siege with vigour. Pompey had his forces construct a wall of circumvallation around the areas held by the Jews and then pitched his camp within the wall, to the north of the Temple. Here stood a saddle allowing access to the Temple, and it was therefore guarded by the citadel known as the Baris, augmented by a ditch. A second camp was erected south-east of the Temple. The troops then set about filling the ditch protecting the northern part of the Temple enclosure and building two ramparts, one next to the Baris and the other on the west, while the defenders, from their superior position, sought to hinder Roman efforts. When the banks were complete, Pompey erected siege towers and brought up siege engines and battering rams from Tyre. Under the protection of slingers driving the defenders from the walls, these began to batter the walls surrounding the Temple. After three months, Pompey's troops finally managed to overthrow one of the Baris towers and were able to enter the Temple precinct, both from the citadel and from the west. First over the wall was Faustus Cornelius Sulla, son of the former dictator and a senior officer in Pompey's army. He was followed by two centurions, Furius and Fabius, each leading a cohort, and the Romans soon overcame the defending Jews. 12,000 were slaughtered, while only a few Romans troops were killed. Pompey himself entered the Temple's Holy of Holies, which only the High Priest was allowed to enter, thereby desecrating it. He did not remove anything, neither its treasures nor any funds, and the next day ordered the Temple cleansed and its rituals resumed. Pompey then headed back to Rome, taking Aristobulus with him for his triumphal procession.
Aftermath
The siege and conquest of Jerusalem was a disaster for the Hasmonean kingdom. Pompey reinstated Hyrcanus II as the High Priest but stripped him of his royal title, though Rome recognised him as an ethnarch in 47 BC. Judea remained autonomous but was obliged to pay tribute and became dependent on the Roman administration in Syria. The kingdom was dismembered; it was forced to relinquish the coastal plain, depriving it of access to the Mediterranean, as well as parts of Idumea and Samaria. Several Hellenistic cities were granted autonomy to form the Decapolis, leaving the state greatly diminished.