Titus was not sure he would be able to conquer the city, which was swollen with pilgrims and refugees to two or three times its usual population, with many of the people willing to die for their cause. He waited, hoping the Sadducees would take control and send a peace delegation, but no delegation arrived. On the day after Passover, Titus started engaging in active warfare.

Now, finally, all the factions in Jerusalem had no choice but to work together and fight their common enemy. Altogether, there were about 23,000 warriors, both Zealots and moderates, as well as many pilgrims who had come for Passover and gotten stuck inside the city. The outnumbered Jewish defenders fought with great courage.

In addition to the many defenders entrenched in the Temple Mount itself, the Jews were concentrated in two more areas:

  1. The Upper City, to the west of the Temple Mount, was the province of the priests and rich people. A deep valley between the Upper City and Temple Mount could be crossed by bridges. Excavations of this area, in the current Old City of Jerusalem, can be toured today.
  2. The Lower City, to the south of the Temple Mount, was the province of the ordinary folk. This area is outside of the current walls of Jerusalem. (Today it is called the City of David – in Arabic, Silwan – and it can also be toured.)

There was also the "New City," a suburb to the north of the city.

The Roman soldiers attacked the weakest side of Jerusalem, the north side, first. They pounded the wall surrounding the New City with their battering rams and threw stones into the city with their catapults. The defenders, from on top of the wall, threw stones and burning torches onto the Romans, occasionally venturing out in surprise attacks to burn the Romans' battle equipment. On the seventh of Iyar, after two weeks of incessant ramming, the Romans breached this wall, and established their camp in the New City.

On the fifteenth of Iyar, after more fierce fighting, they breached a second wall, allowing them access from the north into the Lower City. They did not completely destroy the Lower City at this point. Instead, they paraded in a show of might intended to frighten the Jews. Then they prepared to storm the Upper City and the Temple area.

First they had to take the Antonia fortress, a towering fortress which had been built by Herod overlooking the Temple Mount. The defenders of the Antonia fortress, led by Yochanan of Gush Chalav, were desperate and wily. The Romans built a huge rampart next to the wall, but the Jews dug a tunnel underneath it, filled it with wood, and ignited it. The tunnel collapsed, causing the rampart to collapse as well. The Roman catapults and battering rams were burnt up.