Muslim conquests on the Indian subcontinent mainly took place from the 12th to the 16th centuries, though earlier Muslim conquests made limited inroads into modern Afghanistan and Pakistan as early as the time of the Rajput kingdoms in the 8th century. With the establishment of the Delhi Sultanate, Islam spread across large parts of the subcontinent. In 1204, Bakhtiar Khilji led the Muslim conquest of Bengal, marking the eastern-most expansion of Islam at the time.
Prior to the rise of the Maratha Empire, which was followed by the conquest of India by the British East India Company, the Muslim Mughal Empire was able to annex or subjugate most of India's kings. However, it was never able to conquer the kingdoms in upper reaches of the Himalayas such as the regions of today's Himachal Pradesh, Uttarakhand, Sikkim, Nepal and Bhutan; the extreme south of India, such as Travancore and Tamil Nadu; and in the east, such as the Ahom kingdom in Assam.
Islam in South Asia existed in communities along the Arab coastal trade routes in Sindh, Bengal, Gujarat, Kerala, and Ceylon as soon as the religion originated and had early gained widespread acceptance in the Arabian Peninsula, being brought over by merchants, Sufis and missionaries, who oftentimes settled down and intermarried with the local women, adopting local customs. The first incursion by the new Muslim successor states of the Arab World occurred around 636 CE or 643 AD, during the Rashidun Caliphate,long before any Arab army reached the frontier of India by land.