Prior to Mohammed having his
night visions (or flight) which is referenced in The Koran, in Sura 17:1, which states, "Glory be to Him who made His servant [Mohammed] go by night from the Sacred Mosque to the farthest [or remotest] Mosque", the 'religion' of the middle east consisted of a number of different nature based beliefs, including the worship of the Moon God (or godess) still represented by the Crescent and Star seen atop most Mosques. (Also embodied in the
Ka'ba which houses the
Black Stone, which was revered in Mecca in pre-Islamic times. It became a Muslim relic after Muhammad founded Islam, and pilgrims to Mecca try to stop and kiss it while circumambulating the Ka'ba during the hajj. It is generally believed to be a meteorite.)
"Late Islamic masculinization of the Arabian Goddess, Al-Lat or Al-Ilat - the Allatu of the Babylonians - formerly worshipped at the Kaaba in Mecca. It has been shown that 'the Allah of Islam' was a male transformation of 'the primitive lunar deity of Arabia.' Her ancient symbol the crescent moon still appears on Islamic flags, even though modern Moslems no longer admit any feminine symbolism whatever connected with the wholly patriarchal Allah." (
Source: Payne, Robert; The History of Islam, Dorset Press, NY 1959/1987 )
Space and time aren't sufficient to describe how the Muslim faith spread as a new belief, however you might see
http://san.beck.org/AB13-MuhammadandIslam.html
for a balanced view of the spread of Islam (be prepared for a long read, however)...