Though a Shiite country in an overwhelmingly Sunni region, Iran’s radical Islamism resonates with the politicized Islamism that is energizing most Arab opposition movements, and its militant opposition to the US and support for groups that engage Israel in battle is very popular on the Arab street and in the Arab media. At another level, Iran’s rise, reinforced by its suspected bid for nuclear weapons threatens to awaken historical hostilities, between Sunnis and Shiites and between Persians and Arabs.