From 1000 onwards, Mahmud of Ghazna, a Muslim ruler in central Asia, conducted many raids into India and conquered the Punjab. After Mahmud’s death, and his successors’ defeat by the Seljuqs (1040), the Ghaznavids shifted their power-base to the Punjab, the vanguard of a Muslim invasion of the sub-continent.
The Rajput princes of northern India held off the Muslim invaders for a time, but their resistance was hampered by continual fighting amongst themselves. In due course, several Muslim sultanates established themselves in the north, the Sultanate of Delhi being the most powerful.
In the Deccan, the large Chalukya kingdom broke up into several large states at the end of the 12th century. In south India, the Colas renewed their expansion in dramatic style in the closing decades of the 10th century. They conquered territory both within India and overseas, with expeditions to Sri Lanka and even (according to their records) as far afield as South East Asia. By the early 13th century, however, Cola dominance of southern India is being challenged by other powers, in particular the resurgent Pandya dynasty.
The coming of alien Muslim armies into India seems to have completed the decline of Buddhism in its Indian homeland. It also seems to have started a process whereby Hindus emphasised certain features of their faith, the better to differentiate themselves from the Muslim newcomers. One of these features was caste. From now on, the caste system seems to have started becoming increasingly rigid. This process would continue for several centuries.
The past two and a half centuries have seen, first, the expansion of the Delhi Sultanate throughout India, immediately followed by its rapid disintegration. This process was greatly helped by the sack of the capital, Delhi, in 1398, by the forces of the central Asian conqueror, Timur, invading from Iran. By this date the sultanate is merely one amongst many small states in northern India.
The rise and decline of the Delhi sultanate has left a legacy of Muslim princes ruling in many parts of the sub-continent, along with older Rajput regimes, who have come to an accommodation with their Muslim neighbours. Although much of India is ruled by Muslims, the mass of the population largely remains true to its ancestral Hinduism. For the most part the Muslim rulers do not attempt to impose their own religion of their subjects, and indeed most employ Hindus as senior officials in their governments. In art and architecture, Muslim and Hindu elements are fusing together into a new style which will, in due course, give rise to such wonders as the Taj Mahal.
In the south, two powerful states have been established in the wake of the Delhi sultanate's conquests there. One is the Bahami sultanate, a powerful Muslim state, and the second is the kingdom of Vijayanagra. This is a Hindu state, whose rulers see themselves as the champions of the old religion against the alien forces of Islam. These two states are at almost constant war with one another.