Neither Chandragupta Maurya nor his son Vindusara tried to bring back Kalinga to the Magadha empire. It was Asoka, the son of Vindusara who invaded Kalinga in 261 B.C. and succeeded in occupying Kalinga. The Kalinga War was of colossal nature in which as many as 1,00,000 were killed and 1,50,000 were taken captives while as many as that number died as an aftermath of the war. Asoka was deeply moved by the terrible bloodshed caused by this war and was converted to Buddhism .
The hilly land lying to the west of Kalinga was known as the Atavika territory, the fighting forces of which were utilized by Kalinga during the war. Asoka annexed the coastal region of Kalinga to his empire and gave up the idea of further conquest. He tried to conciliate the unconquered Atavika people and desired to conquer their heart by love. That was the principle of Dharmavijaya and was followed by Asoka after the Kalinga War.
Kalinga became one of the administrative provisions in the empire of Magadha with headquarters of a Kumara (Viceroy) located at Tosali. The second headquarters was at Samapa where a high executive officer called Rajavachanika was stationed. Tosali was also the headquarters of the highest judiciary authority of the province.
Asoka aimed at a benevolent administration with a well organized bureaucracy and vigorously worked for the consolidation of the Maurya rule in the newly conquered province. Buddhism spared over Kalinga under his patronage and became the State religion while the art of stone masonry developed to a great extent. Edicts were engraved on the Dhauli and Jaugada rocks to inculcate his administration and religious principles to the people. Asoka died in 232 B.C. and the Maurya empire lasted up to 185 B.C.