In the 4th century AD, as the Roman empire crumbled,
Christianity gained momentum and Lebanon became part of the eastern
Byzantine Empire, with its capital at Constantinople (modern Istanbul). The
imposition of orthodox Christianity didn't sit well, and when the
Mohammedans brought the word of Allah from the south, they faced little
resistance in Lebanon.
The Umayyuds, the first great Muslim dynasty, held sway in Lebanon for about
a century, but faced opposition from indigenous Jews and Christians,
especially the Syrian Maronite sect who took refuge around Mount Lebanon.
After the Umayyuds fell to the Abbasids in 750, Lebanon became a backwater
of the Persian-flavoured Abbasid Empire. This empire lasted until the 11th
century before being tipped out by the Fatimid dynasty, who struggled on
until the rise of the Crusaders. The Crusaders had their sights set on
Jerusalem, but marched down the Syrian and Lebanese coast, linking up with
the Maronites, before savaging the Holy City.