Part of ancient India and earlier known only as Bengal, Bangladesh had been a fertile alluvial land that attracted outsiders from time immemorial. Thanks to the inherent open-minded nature of Bengalis, the history of Bengal was one that is marked with constant migration and assimilation of outside cultures.
In the proto-historic period, ancient Bengal was believed to be divided among various tribes or kingdoms in the three main regions: Vanga (southern Bengal), Pundra (northern Bengal) and Suhma (western Bengal). While western Bengal, as part of Magadha, became part of the Indo-Aryan civilization by the 7th century BC, the Nanda Dynasty was the first historical state to unify most of Bengal under Indo-Aryan rule.
By the time of reign of the great Indian Buddhist Emperor Ashoka (304?232 BC), Buddhism was firmly entrenched as the number one religion of Bengal. Mahasthangarh, the oldest archaeological site in Bangladesh dating back to 300 BCE, was the ancient capital of the Pundra Kingdom. In the 6th century AD, Sasanka, a powerful Buddhist king, founded the Gauda Empire in Bengal, which was eventually overthrown by the warrior king Sri Harsa, who ruled the Bengal area until the 8th century. Gopala, a Kshatriya tribal chief from Varendra, became the founding figure of the Buddhist Pala dynasty (8th to 11th centuries). He was succeeded by his son Dharmapala, who established the gigantic Somapura Vihara in Varendra, known today as Paharpur.
Though somewhat pushed back in the subsequent centuries, Buddhism never totally died out in Bangladesh. Countrywide it is the third major religion, but in certain areas, such as Chittagong Division, Buddhists make up an impressive 12% of the population.
The Hindu Period:
In the 12th century, Hindu Senas dynasty came to rule Bengal and over-powered Buddhism. Buddhists retreated to the Chittagong area.
The arrival of the Muslims began with a few Sufi (Muslim mystic) missionaries in the 12th century. Then came Mohammed bin Bakhtiar (a Khilji from Turkistan) who, with only 12 men under his command, captured Bengal and brought the area under the rule of the Sultanate of Delhi, the centre of Muslim power in India. Under the Muslims, Bengal entered a new era. Cities developed; palaces, forts, mosques, mausoleums and gardens sprang up; roads and bridges were constructed; and new trade routes brought prosperity and a new cultural life. In 1576 Bengal became a province of the mighty Mughal Empire, which ushered in another golden age in India. Mughal power extended over most of Bengal except the far Southeast around Chittagong, and it was during this period that a small town named Dhaka emerged to become the Mughal Capital of Bengal.