Islam divides the world into regions under its control, the ddr al-Isldm, and regions not subjected as yet, the ddr al-harb. Between this "area of warfare" and the Mushm-dominated part of the world there can be no peace. Practical considerations may induce the Muslim leaders to conclude an armistice, but the obligation to conquer and, if possible, convert never lapses. Nor can territory once under Muslim rule be lawfully yielded to the unbeliever. Legal theory has gone so far as to define as ddr al~ Isldm any area where at least one Muslim custom is still observed. Thanks to this concept, the waging of war acquires religious merit. The Muslim community is under an obligation to combat the infidel.