I can't help it. I'm not judging, I'm just completely bewildered. This ritual is completely foreign to me.

Two groups of 100 men in white robes slashed their heads with long, sharp swords, spraying blood on those near them, to symbolize their anguish over the slaying of Hussein.
Hussein was killed in the Battle of Karbala between a small group of his followers and the Umayyad Army. The Shiites see Hussein and his father, Ali, as the rightful heirs to the prophet, and the battle in which Hussein was killed was one in a series of violent clashes between Sunnis, who disputed the Ali-Hussein claim, and Shiites.

I looked it up, and found that the event in question took place in 680 A.D. You can find more history on the battle here. What I'm not clear on, is the significance or purpose of cutting one's own head open with a sword. Anyone?