Here is an exchange between Todd Caldecott and Max Rodenbeck in the Letters Column of The New York Review of Books, on the latter’s claim (in a previously-published review of Ayaan Hirsi Ali’s Heretic: Why Islam Needs A Reformation), that the Muslim practice of forced conversion was “historically rare” and “revived only recently by ultra-extremist groups such as Boko Haram in Nigeria or ISIS in Iraq.” Caldecott provides, by way of answer, an impressively horrifying list of just some of the recorded instances of mass murder of Hindus in India and the mass destruction of Hindu temples and libraries:
For example, in the thirteenth century, Muhammad bin Bakhtiyar Khilji destroyed the ancient university of Nalanda, killing all the Buddhist monks and nuns, taking literally three months to burn every single book in the university’s library. Imagine if ISIS or al-Qaeda killed everyone on campus at Harvard or Yale, and burned all the lecture halls, libraries, churches, synagogues, and cultural institutions: such was the untold impact on India, in almost every part of India, for a thousand years.
If you are looking for a reason for 'the dark ages' that is a pretty good clue.
Similar examples of forced conversions and brutality can be found during the reigns of Mahmud Khalji of Malwa (1436–1469 AD), Ilyas Shah (1339–1379 AD), Babur (1483–1530 AD), and Sher Shah Suri (1486–1545 AD), all of whom destroyed temples, killed non-Muslims, and forced the conversion of entire communities. Even during the so-called sulah-i-kul (“peace with all”) initiated by Mughal Emperor Akbar (1542–1605 AD), his son Shah Jahan, known for his supposed monument to love, had almost a hundred temples destroyed in the ancient city of Varanasi alone. Jahan’s son Aurangzeb brought an end to any pretense of this institutionalized peace, and went on a rampage, killing Hindus, destroying temples, and placing severe restrictions on already impoverished Hindu cultural institutions.
Caldecott concludes: “Hopefully, in light of this evidence, Mr. Rodenbeck can reevaluate his claim that the forced conversion in Islam is a ‘historically rare practice.'”
In his reply, Rodenbeck concedes the point at once:
Regarding forced conversion and Islam, it is far from my intent to whitewash a long and mixed record. I stand corrected in my injudicious use of the word “rare.” There are indeed numerous instances of forced conversion to Islam…
But then he goes on to insist, backtracking from his backtracking, that in the case of India, the large number of Hindus who remained testify to an absence of “forced conversions.” What they testify to, in fact, is not to Muslim mildness but to the following:
The Hindu population of India was very large, the number of Muslim invaders comparatively very small. Conversion of such numbers took time; what impresses is not how few Hindus became Muslims but how many. There are now 840 million Hindus in historic India (India, Pakistan, and Bangladesh) – lands once almost entirely Hindu (with a small admixture of Buddhists). And there are now 502 million Muslims in historic India (India, Pakistan, and Bangladesh), where at the beginning of the eighth century there were none. Caldecott thinks the more telling figure is that of the 502 million Muslims; Rodenbeck would have us be impressed that the Muslims left so many Hindus alive, which he thinks shows the “absence of forced conversions” rather than being simple testimony to the size of the task.
The definition of “forced conversion” ought to include not only conversion at the point of a sword or a scimitar, but all those conversions by Hindus in India to avoid the jizyah and the host of other disabilities imposed on those Hindus who were allowed to live as a matter of policy. But why were those Hindus allowed to live? Not out of the goodness of Muslim rulers’ hearts, as Rodenbeck implies, but in order to have enough people to continue paying the jizyah, on which the Muslim state relied.
Rodenbeck seems to think that the survival of any non-Muslims under Muslim rule, no matter how few, testifies to Muslim mildness. He swerves from his discussion of India to the East Indies (present-day Indonesia), where he claims – correctly –that on the island of Bali, 85% of the 4 million Balinese are Hindus. But that is the only island, out of hundreds, where the Hindus held out. Surely more meaningful is the fact that Hindus now constitute less than 2%, and Buddhists 0.8%, of the overall population of Indonesia (now 260 million) that, before the Muslim traders arrived, was 100% Hindu and Buddhist.
K. S. Lal and other historians, both Indian and Western, have calculated that more than 80 million Hindus were killed by Muslims during 250 years of Mughal rule in much of India. Rodenbeck does not address this issue of genocide at all. Perhaps, since those tens of millions of Hindus were not subjected to “forced conversion,” he may think these figures are not relevant to the discussion — after all, they were quite dead.
And this discussion didn't even touch on Islam's march across North Africa or the middle east.