When thinking of colonialism and imperialism, I know far more about European adventures than the spread of Islam. I don't know much of the central control structures of the 'ummah'. Like Catholicism (Catholic from Greek katholikos means Universal), there was a belief in a community that was all inclusive as distinct from nation (Sha'b - common ancestry/geography). Much of Africa speaks Arabic, a European Colonial Language, and a very local home language. Even in South Africa, our worst, very local, swear word has Islamic roots. Indonesia is a country that was full of Hindu and Buddhist kingdoms in the 2nd century, Islamic sultanates by the 13th century, European Company rule from 1602, and Colonial rule from 1800. After Japanese occupation in 1942, independence was only secured after World War II in 1945. Today the country of 260 million people is 87% Muslim. There are 300 distinct ethnic groups and 742 different languages. Indonensian has been promoted as the national language since independence but is only the native language of 43 million people. 142 million can speak it as a second language.
The world's largest Buddhist Temple