Mohammedan Middle East, Christianity had grown *in fact, it began in Israel* mostly through people taking it to others, telling them about it, and then letting them choose for themselves whether to believe or not. It was, for the first three or four centuries, able to do so because the Romans held almost the ENTIRE Mediterranean world in sway and could keep roads safe and open *yes, Romans persecuted Christians and Jews, but the persecution pf Christians was more sporadic than one might believe*
Enter Mohammed and Mohammedanism *Islam*: Sword, fire, rapine, slaughter; all of these spread Mohammedanism. Few people chose it for themselves. In fact, Mohammedanism only exists now because it kills anyone who wants to, tries to, or succeeds in, leaving it. One might argue that “Christianity” (Actually Catholicism) did much the same thing, but in fact, the times when they DID so were when particular popes wanted to enforce temporal power.
As for Mohammedans in Europe, Spain and Portugal were overrun by the Mohammedans in the early 700s; France and Western Europe were saved from a similar fate by Charle Martel and the Franks at Tours (Poitiers) in 732. From that point on, the Western Europeans fought a long campaign to drive the Mohammedans back out of Iberia.