From official records of the Sena dynasty it appears that the Senas belonged to the Brahmana-Kshatriya clan of Karnataka in South India. Their remote ancestor was one Virasena, whose name was supposed to have been mentioned in Puranas. According to Dr. Bhandarkar the name Brahmana-Kshatriya was applied to the clans, who were originally Brahmanas and later became Kshatriyas or adopted the profession of Kshatriyas and gradually came to be identified as Kshatriyas. Dr. Bhandarkar also puts that the Senas belonged to that community and Samanta Sena claimed himself a Brahmavadi. The "Deopara Inscription" of the Senas also traces the Sena ancestry from Virasena. Since there are no authentic records available still, a keen controversy prevails among scholars regarding origin of the Senas.
Like the origin of the Senas, their early history or circumstances, which led them to concentrate in Bengal is also still unknown. It has been presumed by historians that the Senas came to Bengal on the eve of the invading army led by the Chalukya kings Vikramaditya VI and Someswara III. Some scholars have also suggested that when Rajendra Chola's army had invaded Bengal, the Senas had accompanied them. According to some other historians, a few Karnataka officials, who were subordinate to the Pala kings, had established their independent kingdom in the region of Radha, taking advantage of the weakness of the Pala powers. Those Karnataka chiefs might have arrived in Bengal in wake of the Chalukya invasion and had settled into a kingdom of their own. According to historians Samantasena was such a chief who had established his independent kingdom in the Radha region of Bengal.
Samantasena was a scion of the Sena family, who had distinguished himself through various warfares in South India. He had settled in Radha in Bengal, at an old age. He had also laid the foundation of the Sena family in Bengal, which had attained sublime success. His son Hemantasena assumed the title "Maharajadhiraja". Hemantasena had carved out an important kingdom in Radha, taking advantage of the disruption of the Pala Empire by the revolt of Divya. From their base in Radha, the Senas ultimately extended their powers over the whole of Bengal.