This chapter discusses the spread of religion in Southern Asia between 711-1400 CE. It covers: 1) The expansion of Islam eastward through Persia, Afghanistan, and into India under the Abbasid Caliphate. 2) The blending of Persian and Islamic culture under the Abbasids, including the establishment of Baghdad as a center of learning and innovation. 3) The decline of the Abbasids due to succession conflicts and the rise of regional powers, though Islamic unity and expansion continued. 4) The Islamic invasions of India by Persian and Ghaznavid warlords and the establishment of the Delhi Sultanate, bringing religious conflict but also connections between Muslims and Hindus