The original idea for the First Crusade that had been preached by Pope Urban II at the Council of Clermont in 1095 had already turned into a much different popular movement, led by Peter the Hermit. Peter's preaching of the Crusade spread much more quickly than the official versions of Urban's call. Peter's version, which probably involved the Second Coming of Jesus Christ, influenced Emich, who spread his own story that Christ had appeared to him. Christ promised to crown him emperor, and would help him convert the Jews of Europe, if Emich would join the Crusade.
He did so, and in the first half of 1096 he gathered an army, which arrived at Speyer in May. Emich, or his followers in separate groups, also went to Worms, Mainz, Cologne, Trier, and Metz, where they forcibly converted the Jewish communities, and massacred those who resisted. Eight hundred Jews were killed at Worms alone. Peter the Hermit's mob massacred communities in other cities as well.
Emich was apparently motivated by greed, as he needed money to finance his army, and the Jewish communities were known to be wealthy. He also seems to have felt that the Jews were just as much enemies of Christ as the Muslims in Syria, but the Jews were more familiar and closer to home. The Jews in the cities along the Rhine at first attempted to pay Emich to make him go away, but although he accepted their money, he still converted or killed them. In some communities, mothers were said to have killed their own children to avoid the inevitable slaughter. The Christian bishops of the cities often attempted to protect their Jewish subjects, but were not always successful.
Emich's army attracted many strange followers, including a group who worshipped a duck they believed to be filled with the Holy Spirit. The army continued down the Rhine until they reached the Danube, which they followed to Hungary. Here, after having run out of money and food, they began to pillage Hungarian land. Much of the army was killed by the Hungarians; the rest split up to join the other Crusader armies, and Emich went back home to Leningen, where he was scorned for not fulfilling his vow to capture Jerusalem.