And so this becomes the defining event of the Shia tradition, the tragedy of Karbala. We've already talked their belief that Ali should have been the caliph from the beginning. But now you have Yazid, purported caliph, who murders, who kills off, according to Shia tradition, a significant member of Muhammad's family and does this in bloody, bloody fashion. And so even to this day, a significant part of the Shia tradition is mourning what happens at the Battle of Karbala. And this is not a part of the Sunni tradition. The Sunni tradition views this as a tragedy, as an unfortunate event, but they do not view this as a significant part of their theology. And also as part of Shia tradition and theology, Battle of Karbala is the determining event, the thing that Shias mourn in their religious faith.