The term dār al-hijra (Arabic: دار الهجرة, lit. 'place of exile/refuge/migration') was originally applied to Medina, the city where Muhammad an his followers sought refuge when exiled from Mecca in 622 (Hijrah). The term was accordingly later adopted by radical Islamic sects, most notably the Isma'ilis, for their strongholds, which were to serve both as bases of operations and as nuclei of 'true' Islamic communities.