A Gradual Process. It is often wrongly imagined that as soon as any country came under the political rule of Muslims or a Muslim state, a majority, or even all, of its population started professing Islam as their personal religion, whether from choice or compulsion. In actuality, the spread of Islam as a religion in a particular country has always been a gradual, slow process that has taken decades or, most often, centuries. In fact, this process is still ongoing in most Muslim-majority countries, where there exist religious minorities whose numbers have slowly dwindled over the centuries, often from a point at which their faith was the majority religion.

No Compulsion in Religion. The Qur'an specifies, "There is no compulsion in religion" (2: 256), a statement recognizing that no one can ever be forced to believe anything and commanding Muslims never...