Jerusalem was held by Arab, not Turkish, defenders. Inside the city, too, were a large number of Jews and Christians, who were tolerated by their Arab rulers. But Jerusalem was not well defended, and no Arab lord from Damascus or Cairo or Bagdad was willing to come to its rescue.
The crusaders besieged Jerusalem for a month, and were in turn assaulted by wind and heat. They very quickly managed to pollute the best water sources, thereby rendering themselves even more miserable. Siege engines could be built only by dragging great logs from the distant mountains, harassed by Arab marauders all the while.
It was discouraging and more than discouraging: why had God granted them such victories, only to deny them the final prize?
The priests in the army had an answer: God would not allow them to liberate the city because the army was guilty of great sins. There was gambling and prostitution and theft and worse rampant in the ranks of the crusaders, and such men could not liberate the Holy Sepulcher.
So, early in July, the Christian army underwent a three day fast. At the end of it, on 8 July, they marched around the city on a footpath in a complete circuit, bishops and priests in front, with crosses and relics, then princes and knights, then soldiers and pilgrims. All were barefoot, and they sang psalms as they went. And the Muslims jeered from the walls. The penitent crusaders then ascended the Mount of Olives and listened to inspired sermons.