This article records tradition as it has been passed down and reported. Its sources are not yet part of the atlas's verified catalogue.
Islam reaches Syria through a military campaign that opens the region to Rashidun rule rather than through preaching alone. The campaign began in 634, Rashidun forces advancing under commanders including Khalid ibn al Walid, and it reached its decisive moment in August 636 at the Battle of Yarmouk, where those forces defeated the Byzantine army in the engagement that ended Byzantine rule in Syria for good.
Khalid ibn al Walid carried the military leadership of the campaign, and the victory at Yarmouk was not one skirmish among many but the single battle that broke Byzantine resistance in the region. What followed was rapid: with the Byzantine army defeated, Syria's cities and countryside came under the Rashidun Caliphate's administration in the years immediately after, without a comparable second stand.
What changed for Islam's spread is the addition of one of the wealthiest and most populous provinces of the former Byzantine world to the new caliphate, barely more than a decade after Muhammad's own community had been established at Medina. Syria's fall opened the eastern Mediterranean to the same expansion that would carry Rashidun rule into Egypt and Persia within the same generation.