Bengal region is known the history only after the Gupta period (320-520 AD).
The Guptas ruled this region from Magadh (modern Bihar) and the period was the golden age of India. After the decline of the Guptas, the kingdom of Gaur in Bengal became well known.
Sasanka (606 AD) was the first known independent ruler of Bengal. The history of Bengal after the death of Sasanka to the reign of the king
Gopala is uncertain. Gopala was a kshatriya and was a military general. Gopala was selected by the people, as the king In 750 AD, who put an end to chaos in the country. This led to foundation of the Pala dynasty in Bengal.
Dharmapala (770 - 810 AD) succeeded by his father Gopala. Having inherited a sound and stable empire from his father, Dharmapala found himself comfortable in a position to take a foreign expedition. Though succeeded initially, got caught in the conflict between the Pratiharas and the Rashtrakutas. Pratihara ruler Vatsaraja defeated Dharmapala and the territory of Bengal got digested in Pratiharas empire. But the luck was still in favour of Dharmapala, the Rashtrakuta ruler Dhruva defeated Dharmapala and gained Dharmapala more than what he had lost to Pratiharas! The history recurred again when the next Pratihara ruler Nagabhata-II defeated him. Govinda-III, the Rashtrakuta ruler was the next rescuer to Dharmapala in disguise, when Govinda-III had returned to Deccan soon after the victory over Pratiharas.
Devapala (810 - 850 AD)(shifted capital to Monghyr) was succeeded by his son Devapala. A worthy son of a deserving father not only maintained what he inherited, but also expanded his territory. Devapala was a threat to the Pratihara rulers namely Ramabhadra and Bhoja. It is also known that Amoghavarsha, the Rashtrakuta ruler was defeated by Devapala. Devapala, the great patron of Buddhism, constructed many temples and monarchies in Magadha.
Narayanapala (850 - 908 AD) : The reign of Narayanpala (reign 854-908) witnessed the beginning of the dynasty's decline. A man of pacific and religious disposition was defeated by the Pratiharas. Sometime after 860 AD, the Rashtrakutas defeated him. At the same time, the Pratiharas were weak too, following revolts; and the Rashtrakuta ruler Krishna-II defeated the Pratihara ruler. With the conflicts between the Pratiharas and the Rashtrakuts, Narayanapala was able to establish his supremacy in Bengal and Bihar, thus reigning for nearly half a century.
Narayanapala was succeeded by Rajyapala,
Rajyapala by Gopala-II and Vigrahapala subsequently to reign Bengal for nearly eighty years.
Mahipala I's (reign 988-1038) reign saw a period of ascendancy for the Pala power. He managed to regain the lost conquests of earlier Palas. But this time, he had to face CHOLAs of the south. Though Rajendra Chola defeated king Mahipala-I, but the interest of Chola was to take the sacred water of Ganges in order to purify his own country by crossing Bengal ! Though Mahipala was saved in this Chola's expedition, he faced an invasion by the Kalachuri king Gangeyadeva.
Mahipala - I was succeed by Nayapala in about 1038 AD.
Vigrahapala-III succeeded Nayapala in about 1055 AD. The constant conflict between Kalachuris and the Palas was contained by the alliance between Kalachuri and Palas. It is stated that Vigrahapala-III was in possession of Gauda and Magadha shortly before 1068, it was the same time, he suffered a defeat in the hand of new force of Deccan, the Chalukyas.
It was during the next ruler Mahipala-II, the feudatories became powerful. Number of his vassals combined and defeated Mahipala-II and Divya, an officer of the state brought about the death of Mahipala-II.
The next rulers, Ramapala
(Sandhyakara Nandi's Ramacharita is an eulogy to him& mentions the Kaivarta Peasants rebellions),
Kumarapala .... could not arrest the decline of the dynasty.
The Pala dynasty which rose to the rank of the foremost imperial power saw his end in the hand of the last ruler Govindapala in about 1175 AD.