What was the Children's Crusade?

The Crusading movement (the movement to take back the Holy Land from the Muslims and Turks) in Europe in the Middle Ages was religious as well as political and military. A lot of people focused only on the religious aspects and got carried away by them. In the year 1212, 2 teen boys (Stephen of Vendome, Nicholas of Cologne) who imagined they were instructed by Jesus preached a Crusade to children and poor people to walk to Jerusalem and God would deliver it to them. Up to 30,000 children, teens and poor left their European villages following the two. Of course the whole thing was a fake, scam and disaster Stephens group reached Marseilles on the south coast of France and were sold as slaves to the Muslims of North Africa. Nicholas's group was turned back by the Italians at Genoa who told them to go back to Germany. Some modern day historians think maybe it never happened, but it's consistently recorded well enough over the centuries to think it may have.