Mahdi Army 'lay down' arms

Juan Cole attempts to figure out why:

In the aftermath of the fighting Tuesday in the holy city of Karbala between the Mahdi Army and the Badr Corps of the Supreme Islamic Iraqi Council, and then attacks on SIIC offices in Baghdad by Mahdi Army fighters, the militia's leader, Muqtada al-Sadr, called Wednesday for it to lay down its arms for 6 months.

My guess is that Muqtada realizes that his men went too far, in trying to take the shrine of Imam Husayn by main force, and in disrupting a major Shiite festival. These actions would be highly unpopular in the Shiite street, and could cost Muqtada some of his otherwise impressive popularity in the South. Aljazeera showed him speaking in Najaf, by the way, putting the lie to Bush administration allegations that he had gone into hiding in Iran (that was just a smear, since he prides himself on his Iraq nationalism).

Al-Hayat reports in Arabic that Muqtada said: "We considered it beneficial to freeze the Mahdi Army without exception, in order to rebuild its structure in such a way as to preserve its doctrinal heading-- for a period of 6 months from the issuing of this decision." He added, "We also announce three days of mourning, and the closing of the offices of the Martyr Sadr throughout Iraq, the wearing of black, the holding of mourning sessions." He urged the public to investigate what had occured in Karbala. Link