For instance, today, more Muslims live in Indonesia than in any other country. And yes, I know Indonesia has more than two islands. It's not to scale, obviously. Knowing what you've already learned about the growth of Islam and the spread of trade, it won't surprise you to learn that Islam spread to Indonesia via the monsoon marketplace. After the 1200s, the region, which had previously been heavily influenced by the Indian religions of Hinduism and Buddhism, like witness this temple, for instance, became increasingly Islamic as rulers and elites adopted the religion so they could have religious as well as economic ties to the people they were trading with. The conversion of most of a region to Islam, where it continues to flourish today, is a pretty big deal. But Islam didn't spread as effectively to Thailand, Laos, Cambodia, or Vietnam because they weren't centers of trade.