In recent years a tradition of walking 80km from Najaf (the resting place of Ali the father of Hussain) to Karbala has been reignited. Every year since, the number has been rising steadily from 17 million pilgrims to at least 25 million. People from all walks of life and all corners of the globe make the journey, despite the imminent threat of terrorists who have vowed to attack the pilgrims.