Following Pope Urban's speech at Clermont Peter the Hermit, a simple man with a powerful ability to move people by his words, started preaching for Christians to help their fellow Christians in the East. He started to gain a large number of followers eager to go to Jerusalem with promises of absolution and freedom from a life of hunger and depravation. His followers were poor, not prepared for the journey and not armed.

Peter the Hermit's army of ordinary people was large and it needed feeding. One of the more noble members of the army was Walter Sans Avoir, also known as Walter the Penniless. When the army reached Cologne in April Peter decided to halt the army to take advantage of the good supply of food. Walter was impatient and with a small section of the army continued on. They passed through Hungary but at the town of Semlin a dispute broke out when some of his men stole food. When his men were refused food at Belgrade because the harvest had not yet been gathered Walter's army began pillaging the surrounding area. Finally Alexius Comnenus sent supplies and an escort to guard the Crusaders as they marched to Constantinople. The guard ensured that the Crusaders didn't cause any more trouble.

At Constantinople the Emperor Alexius welcomed Peter's army but there were too many people and no provision had been made for them. There was a general lack of discipline that resulted in repeated attacks and thefts from surrounding villages. Alexius warned Peter to wait for better trained troops to arrive before moving on but the pressure of the army was so great on Constantinople that they were forced to move before help could arrive.