The ‘Big Bang’ of the Umayyad Caliphate carried Islam by conquest from Spain to India in the century after Muhammad’s death. These dominions commanded the major trade routes of Europe, Asia and Africa; Islam’s further expansion owed as much to its long period of cultural and commercial hegemony as to military power. The Ottomans went on to absorb and partially convert the former territories of the Byzantine Empire, and the Mughals unified most of India under Islamic rule. However, for a time Islam faced wholesale reversal by the Mongol invasions of the 13th century. It won the argument, rather than the war, by achieving the conversion of most of the Mongol khanates over time thus spreading Islam deep into central Asia. Commercial contact was key to the formation of a cluster of Islamic states on the southern borders of the Sahara, and the east coast of Africa.