Some 140 Iranian and Iraqi Shiite pilgrims died earlier this week in suicide bombings in Baghdad and Karbala, and another 43 Pakistani Shiites were killed in Quetta, Pakistan. Moreover, yesterday, Shiite Muslims in Iraq refused to sign the U.S. sponsored Iraqi Constitution unless changes are made to strengthen Shiite power. These developments highlight a grave problem that confronts American foreign policy — i.e., the conflict between Shiite Muslims and Sunni Muslims in Iraq threatens a religious war throughout Muslim regions of the Middle East and Asia. In this David Warren piece and in this Vali Nasr piece, Mr. Warren and Professor Nasr examine Wahhabi Sunni Muslim antipathy toward Shiite Muslims, and the growth of the conflict between those two factions of Islam over the past decade. These are excellent analyses of this primary barrier to stability in Islamic countries.