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 arises in Mecca when Muhammad's first reported revelations come to him in and around the city beginning around 610 CE, a date this atlas records as debated within roughly that range rather than fixed to a single year. Over the following decade a small community of followers gradually gathered around him there, drawn to the message even as it grew increasingly unwelcome to Mecca's own leadership.
No single dramatic event carries this period the way a battle or a formal embassy might; it is Muhammad's own decade of preaching, one convert at a time, against mounting opposition from Mecca's Quraysh leadership, the tribe that controlled the city and its trade. That opposition would eventually make Mecca untenable for the new community, but across this founding decade Mecca is where the message itself first took shape and where its first hearers first accepted it.
What this period represents for Islam's spread is the origin point itself, prior to the emigration to Medina in 622 that marks the end of this phase and, by tradition, year one of the Islamic calendar. Everything that follows, the political community at Medina, the campaigns that carried Islam across Syria, Egypt, Persia and beyond, begins with this decade of revelation and gathering in Mecca.