Well, I overstated it. His consolidation of the Arabian peninsula was certainly by force of arms, including some Jewish Arab tribes around Medina. After his death, Islam became more or less a coalition of Arab tribes. In fact, the original name was, translated, "the Arab Religion." However, after they enveloped nearby lands, they were faced with a new dilemma - Islamic converts, largely volunteers among the wealthier classes, to escape the "poll tax" and other limitations on non-Muslims (think Kosovo). Initially, they had no name for these converts (the original Muslims were designated by tribe). They invented a new class for these converts, but were happy to coexist with Jews and Christians, so long as they obeyed the restrictions and paid the extra non-Muslim taxes. In southern Iberia, they were invited in by Arian Christians (similar to today's Unitarians), who rejected the Holy Trinity theology altogether. They "conquered" all of today's Spain and Portugal with an absurdly small army. So, no, they weren't originally a proselytizing religion at all, rather clannish, in fact. That, of course, is not the case today. This is far too long, but the history of Islam and what it's become is fascinating...