Islamic missionary activity

Dawah, Islamic missionary work, means to "invite" (in Arabic, literally "calling") to Islam, which is estimated to be the second-largest religion, after Christianity. After the death of the Islamic prophet Muhammad, from the 7th century onwards, Islam spread rapidly from the Arabian Peninsula to the rest of the world through either trade and exploration or Muslim conquests. The purpose of Islamic missionary activity is to deliver the message revealed by God through Prophet Muhammad to the world.

Following the death in 632 AD of Muhammad, Islam spread far and wide within a very short period, much of this occurring through an initial establishment and subsequent expansion of an Islamic Empire through conquest, such as that of North Africa and later Spain (Al-Andalus), and the Islamic conquest of Persia putting an end to the Sassanid Empire and spreading the reach of Islam to as far east as Khorasan, which would later become the cradle of Islamic civilization during the Islamic Golden Age and a stepping-stone towards the introduction of Islam to the Turkic tribes living in and bordering the area.

The Arab Christian Bedouins embraced Islam following the wake of the Battle of al-Qādisiyyah in which the Sassanids were routed. A brotherhood developed between Arabs, including non-Muslims many of whom voluntarily aided the Muslims in their military expeditions. Some Christians saw the success of the Muslim conquests as divine intervention in that God would grant victory to his favored servants. During the rule of Umar II and Al-Ma'mun, Islam gained numerous converts, as the rulers sent letters to distant areas and held debates.

...
Wikipedia