The pilgrimage is to commemorate the martyrdom of Imam Musa al-Kadhim, one of the 12 Imams of Shia Islam.

CNN: Three U.S. soldiers killed in Iraq

It was not an act of martyrdom, or of arrogance or self-delusion, but, rather, an exercise in intellectual consistency.

NEWYORKER: Deceptive Picture

It celebrates the end of the 40-day Ashura period honoring Hussein's martyrdom.

CNN: Pilgrims flood Karbala on final holy day

They regard the denial of Ali's alleged right to succeed the prophet on his death, his subsequent murder, and the martyrdom of his son Hussein at Karbala (in present-day Iraq) later as seminal events.

WSJ: Sadanand Dhume: The Plight of Pakistan's Shia