The wholesale conversion to Islam of the population of what was to become Bangladesh began in the thirteenth century and continued for hundreds of years. Conversion was generally collective rather than individual, although individual Hindus who became outcastes or who were ostracized for any reason often became Muslims. Islamic egalitarianism, especially the ideals of equality, brotherhood, and social justice, attracted numerous Buddhists and lower caste Hindus. Muslim missionaries and mystics, some of whom were subsequently regarded as saints (usually known as pirs in Bangladesh) and who wandered about in villages and towns, were responsible for many conversions.

Most Muslims in Bangladesh are Sunnis, but there is a small Shia community. Most of those who are Shia reside in urban areas. Although these Shias are few in number, Shia observance commemorating the martyrdom of Ali's sons, Hasan and Husayn, is widely observed by the nation's Sunnis.

The tradition of Islamic mysticism known as Sufism appeared very early in Islam and became essentially a popular movement emphasizing love of God rather than fear of God. Sufism stresses a direct, unstructured, personal devotion to God in place of the ritualistic, outward observance of the faith. An important belief in the Sufi tradition is that the average believer may use spiritual guides in his pursuit of the truth. These guides - friends of God or saints - are commonly called fakirs or pirs. In Bangladesh the term pir is more commonly used and combines the meanings of teacher and saint. In Islam there has been a perennial tension between the ulama - Muslim scholars - and the Sufis; each group advocates its method as the preferred path to salvation. There also have been periodic efforts to reconcile the two approaches. Throughout the centuries many gifted scholars and numerous poets have been inspired by Sufi ideas even though they were not actually adherents.

Sufi masters were the single most important factor in South Asian conversions to Islam, particularly in what is now Bangladesh. Most Bangladeshi Muslims are influenced to some degree by Sufism, although this influence often involves only occasional consultation or celebration rather than formal affiliation. Both fakirs and pirs are familiar figures on the village scene, and in some areas the shrines of saints almost outnumber the mosques. In some regions the terms fakir and pir are used interchangeably, but in general the former connotes an itinerant holy man and the latter an established murshid, a holy man who has achieved a higher spiritual level than a fakir and who has a larger following.

Ever since Sufism became a popular movement, pious men of outstanding personality reputed to have gifts of miraculous powers have found disciples (murids) flocking to them. The disciple can be a kind of lay associate earning his living in secular occupations, consulting the pir or murshid at times, participating in religious ceremonies, and making contributions to the support of the murshid. In addition, he may be initiated into a brotherhood that pledges its devotion to the murshid, lives in close association with him, and engages in pious exercises intended to bring about mystical enlightenment.

The Qadiri, Naqshbandi, and Chishti orders were among the most widespread Sufi orders in Bangladesh in the late 1980s. The beliefs and practices of the first two are quite close to those of orthodox Islam; the third, founded in Ajmer, India, is peculiar to the subcontinent and has a number of unorthodox practices, such as the use of music in its liturgy. Its ranks have included many musicians and poets.

Pirs do not attain their office through consensus and do not normally function as community representatives. The villager may expect a pir to advise him and offer inspiration but would not expect him to lead communal prayers or deliver the weekly sermon at the local mosque. Some pirs, however, are known to have taken an active interest in politics either by running for public office or by supporting other candidates. For example, Pir Hafizi Huzur ran as a candidate for president in the 1986 election. The pirs of Atroshi and Sarsina apparently also exerted some political influence. Their visitors have included presidents and cabinet ministers.

Although a formal organization of ordained priests has no basis in Islam, a variety of functionaries perform many of the duties conventionally associated with a clergy and serve, in effect, as priests. One group, known collectively as the ulama, has traditionally provided the orthodox leadership of the community. The ulama unofficially interpret and administer religious law. Their authority rests on their knowledge of sharia, the corpus of Islamic jurisprudence that grew up in the centuries following the Prophet's death.

The members of the ulama include maulvis, imams, and mullahs. The first two titles are accorded to those who have received special training in Islamic theology and law. A maulvi has pursued higher studies in a madrasa, a school of religious education attached to a mosque. Additional study on the graduate level leads to the title maulana.

Villagers call on the mullah for prayers, advice on points of religious practice, and performance of marriage and funeral ceremonies. More often they come to him for a variety of services far from the purview of orthodox Islam. The mullah may be a source for amulets, talismans, and charms for the remedying of everything from snakebite to sexual impotence. These objects are also purported to provide protection from evil spirits and bring good fortune. Many villagers have implicit faith in such cures for disease and appear to benefit from them. Some mullahs derive a significant portion of their income from sales of such items.

In Bangladesh, where a modified Anglo-Indian civil and criminal legal system operates, there are no official sharia courts. Most Muslim marriages, however, are presided over by the qazi, a traditional Muslim judge whose advice is also sought on matters of personal law, such as inheritance, divorce, and the administration of religious endowments (waqfs).

In the late 1980s, the ulama of Bangladesh still perceived their function as that of teaching and preserving the Islamic way of life in the face of outside challenges, especially from modern sociopolitical ideas based on Christianity or communism. Any effort at modernization was perceived as a threat to core religious values and institutions; therefore, the ulama as a class was opposed to any compromise in matters of sharia. Many members of the ulama favored the establishment of an Islamic theocracy in Bangladesh and were deeply involved in political activism through several political parties. Most members of the ulama were also engaged in carrying on the tabliqh (preaching movement), an effort that focuses on the true sociopolitical ideals of Islam and unequivocally discards all un-Islamic accretions. Tabliqh attracted many college and university graduates, who found the movement emotionally fulfilling and a practical way to deal with Bangladesh's endemic sociopolitical malaise.

A number of Islamic practices are particular to South Asia, and several of them have been subject to reforms over the years. For example, the anniversary of the death of a pir is observed annually. Popular belief holds that this anniversary is an especially propitious time for seeking the intercession of the pir. Large numbers of the faithful attend anniversary ceremonies, which are festive occasions enjoyed by the followers of the pir as well as orthodox Muslims. The ceremonies are quite similar in form and content to many Hindu festivals. Several nineteenth- and twentieth-century fundamentalist reform movements, aimed at ridding Islam of all extraneous encroachments, railed against these and similar practices. Nevertheless, the practice of pir worship continued unabated in the 1980s.

Nonorthodox interpretations of Islamic beliefs and practices pervaded popular religion in Bangladesh in the 1980s. Hindu influences can be seen in the practice of illuminating the house for the celebration of Shabi Barat (Festival of the Bestowal of Fate), a custom derived from the Hindu practices at Diwali (Festival of Lights). Rituals to exorcise evil spirits (jinni) from possessed persons also incorporated Hindu influence. Often, villagers would fail to distinguish between Hindu and Muslim shrines. For example, shrines called satyapir, which dot rural Bangladesh, are devoted to a Hindu-Muslim synthesis known as Olabibi, the deity for the cure of cholera. This synthesis is an intriguing superimposition of the Hindu concept of divine consort on the stern monotheistic perception of Allah.

Post-1971 regimes sought to increase the role of the government in the religious life of the people. The Ministry of Religious Affairs provided support, financial assistance, and endowments to religious institutions, including mosques and community prayer grounds (idgahs). The organization of annual pilgrimages to Mecca also came under the auspices of the ministry because of limits on the number of pilgrims admitted by the government of Saudi Arabia and the restrictive foreign exchange regulations of the government of Bangladesh. The ministry also directed the policy and the program of the Islamic Foundation, which was responsible for organizing and supporting research and publications on Islamic subjects. The foundation also maintained the Bayt al Mukarram (National Mosque), and organized the training of imams. Some 18,000 imams were scheduled for training once the government completed establishment of a national network of Islamic cultural centers and mosque libraries. Under the patronage of the Islamic Foundation, an encyclopedia of Islam in the Bangla language was being compiled in the late 1980s.

Another step toward further government involvement in religious life was taken in 1984 when the semiofficial Zakat Fund Committee was established under the chairmanship of the president of Bangladesh. The committee solicited annual zakat contributions on a voluntary basis. The revenue so generated was to be spent on orphanages, schools, children's hospitals, and other charitable institutions and projects. Commercial banks and other financial institutions were encouraged to contribute to the fund. Through these measures the government sought closer ties with religious establishments within the country and with Islamic countries such as Saudi Arabia and Pakistan.

Although Islam played a significant role in the life and culture of the people, religion did not dominate national politics because Islam was not the central component of national identity. When in June 1988 an "Islamic way of life" was proclaimed for Bangladesh by constitutional amendment, very little attention was paid outside the intellectual class to the meaning and impact of such an important national commitment. Most observers believed that the declaration of Islam as the state religion might have a significant impact on national life, however. Aside from arousing the suspicion of the non-Islamic minorities, it could accelerate the proliferation of religious parties at both the national and the local levels, thereby exacerbating tension and conflict between secular and religious politicians. Unrest of this nature was reported on some college campuses soon after the amendment was promulgated.