July 20, 70:
Titus, son of Roman Emperor Vespasian, storms the Fortress of Antonia north of the Temple Mount in Jerusalem during the Siege of Jerusalem. In the process, Romans are drawn into street fights with Zealots.
Jews had reoccupied most of Jerusalem from the Romans in 66. After this, the Zealots mostly fought amongst themselves, since they lacked good leadership, discipline and training and preparation for battles.
Titus surrounded Jerusalem in 70, accompanied by three legions, while a fourth set up near the Mount of Olives. He let pilgrims enter the city to celebrate Passover, and then refused to let them leave, intending to pressure the Zealots into capitulation.
The Jews responded by killing several Roman soldiers and Titus sent Flavius Josephus, a Jewish historian, to negotiate with the Zealots. He was wounded with an arrow, and Titus launched a sudden attack on the city, during which he was nearly captured.
In mid-May 70, Titus tried to destroy the Third Wall with a ram, breaching it and the Second Wall, and heading for the Fortress of Antonia. The Zealots and Romans began having street battles, with the former retreating to avoid heavy losses. Josephus tried again to negotiate, but Jewish attacks prevented construction of siege towers at the Fortress. The situation became more desperate in Jerusalem, since food and water were running low.
On July 20, 70, the Romans launched a secret attack on the Fortress, overwhelming the Zealots, who were sleeping at the time. After they had taken the Fortress, the Romans began using it as a launch pad for an attack on the Temple, setting it on fire. Titus only wanted to seize the Temple and transform it into a place of worship dedicated to the Roman Emperor and gods, but it soon was destroyed. The fire soon spread throughout the city.
The day of the Temple’s destruction is now known as Tisha B’Av, and is marked by Jews worldwide as a day of mourning.
The Romans then moved to crush the Jewish resistance. Some escaped through underground tunnels, while others faced off against the Romans in the Upper City. The Romans had completely retaken the city by September 7, and the Romans continued to hunt down Jews who had fled.
Josephus claims 1,100,000 people were killed in the Siege of Jerusalem, most of whom were Jewish. Of these, he says 97,000 were captured and enslaved. Many Jews fled to areas around the Mediterranean that weren’t occupied by the Romans.