Peter the Hermit was a popular preacher from present day Belgium and began the first battle of the the First Crusade. He ignored the Pope's command and left to Constantinople to gain help, however, during this time the People's crusades were killed by the Turks. The Seljuk Turks were the victors of this battle and killed between 17,000 and 25,000 crusaders.
Six months following the Battle of Antioch the crusaders marched to Jerusalem and were prepared for battle. The Turks lost, and an estimated 28,000 to 45,000 soldiers and inhabitants were killed. This battle allowed the crusaders to take control of Jerusalem which was an important holy site to both Christians and Muslims.
This was the last action of the first crusades and happened after the fall of Jerusalem. This was a surprise attack and led to the crusaders winning the First Battle of the Crusades. This later resulted in the rise of antisemitism which was prejudice towards Jews.