The earliest historical reference to organized political life in the Bangladesh region is usually traced to the writings on Alexander's invasion of India in 326 B.C. The Greek and Latin historians suggested that Alexander the Great withdrew from India anticipating the valiant counter attack of the mighty Gangaridai and Prasioi empires which were located in the Bengal region. It is not, however, clearly known who built these empires.
Literary and epigraphic evidence refer to the rise and fall of a large number of principalities in the region which were variously known as Pundra Vardhana (northern Bangladesh), Gauda (parts of West Bengal and Bangladesh), Dandabhukti (southern West Bengal), Karna Subarna (part of West Bengal), Varendra (northern Bangladesh), Rarh (southern areas of West Bengal), Summha Desa (south-western West Bengal), Vanga (central Bangladesh), Vangala (southern Bangladesh), Harikela (North-East Bangladesh), Chandradwipa (Southern Bangladesh), Subarnabithi (central Bangladesh), Navyabakashika (central and southern Bangladesh), Lukhnauti (North Bengal and Bihar) and Samatata (Eastern Bangladesh)
There are two schools of opinion regarding the political evolution of ancient Bengal. According to one school, the Bangladesh region in the ancient period was an integral part of mighty empires in north India. These historians maintain Gangaridai and Prasioi empires were succeeded by the Mauryas (4th to 2nd century B.C.), the Guptas (4th-5th century A.D.), the empire of Sasanka (7th century A.D.), the Pala empire (750-1162 A.D.), and the Senas (1162-1223 A.D.). Specially, the Pala empire which lasted for more than four hundred years and reached its zenith in eighth and ninth centuries under the leadership of Dharmapala and Devapala is cited as an example of Bengal's political genius.
The revisionist historians are of the opinion that the traditional interpretation overstates the role of all-India empires in the political life of the Bangladesh region. They maintain that epigraphic evidence suggests that only some of the areas which now constitute Bangladesh were occasionally incorporated in the larger empires of South Asia. In their view, political fragmentation and not empire was the historical destiny of Bangladesh region in the ancient times. Inscriptions attest to the existence of a succession of independent kingdoms in southern and eastern Bengal. These local kingdoms included the realms of Vainyagupta (6th century), the Faridpur kings (6th century), the Bhadra dynasty (circa 600-650 A D), Khadaga dynasty (circa 650-700 AD), Natha and Rata dynasty (750-800 A D ), the rulers of Harikela (circa 800-900), Chandra dynasty (circa 900-1045 A D), Varman dynasty (circa 1080-1150 A D), and Pattikera dynasty (circa 1000-1100 A D).
pinions differ on the reasons for political fragmentation in Bengal. Some scholars attribute it to Bangladesh's topography specially to difficulties in negotiating its swamps and marshes, its unending maze of rivers and creeks and dislocations caused by the Bengali rainy season. Others emphasize the frontier character of the region which attracted from north India a continuous stream of rebel, heretics, and malcontents who destabilized the political life. Some scholars maintain that political fragmentation was fostered by a lack of corporate life at the village level. Specially, the village organizations were weakest in the eastern and southern areas; the corporateness of villages gradually increased in the western areas. Political fragmentation was, therefore, endemic in eastern and southern areas which now constitute Bangladesh.
The primacy of the individual in social life and the concomitant institutional vacuum in Bangladesh region was not, however, an unmitigated shortcoming. The weakness of social, political and economic institutions provided a congenial environment for freedom of religion. The Buddhist rulers continued to rule Bengal long after the resurgence of Brahmanism in the rest of north India. Nowhere in South Asia were the deviations from the Brahmanical orthodoxy so glaring as in the Bengal zone. The esoteric cults like Vajrayana, Shajayana, Kalachakrayana, Nathism, the Bauls and the folk cults flourished in pre-Muslim Bengal. Throughout history, small kingdoms blossomed and withered like wild flowers in this region. In an environment characterized by weak political institutions, heresy, heterodoxy and alien faiths thrived in defiance of the Brahmanical orthodoxy.