God's way of bringing believers to faith and the means by which prophets call individuals and communities back to God. Many interpret dawah as calling Muslims back to the purer form of religion practiced by Muhammed and the early Muslim community. Historically, missionary dawah accompanied commercial ventures or followed military conquests. Dawah was also the function of the caliph, extending authority over Muslims outside Islamic lands and promoting Islamic unity. In the twentieth century, dawah has become the foundation for social, economic, political and cultural activities as well as domestic and foreign policy strategies; jusitification for breaking away from the secular and colonial West; legitimation for claims to independent authority within the nation-state; and a call to membership in the righteous Islamic community.