Kalinga war is one of the deadliest wars in the history of warfare. It was fought in the year 261 B.C. between the rulers of Kalinga and the Magadhan king Ashoka in the eighth year of latter’s coronation and continued till the 10th year of his reign. History has not recorded the name of the Kalingan ruler who fought this valiant war against the mighty Magadhans. It is believed that Kalinga was an independent Republic corresponding to modern Orissa which was ruled by an elected council.

The definite causes which prompted Ashoka to wage a war against Kalinga are not very clear. The reasons recorded by historians are many. The first and foremost cause was the expansionist policy of Ashoka. Kalinga was the only independent country in the immediate neighbourhood of Magadha. Ashoka and his predecessors had conquered the whole of north India except Kalinga. Without the occupation of Kalinga, Magadhan Empire was incomplete. Further, Kalinga posed a constant threat to Magadha with its military strength and followed policy hostility to Magadha. The Kalinga rulers regularly increased their military prowess from time to time and allied itself with the Chola and Pandya countries of the south which were known enemies of Magadha. According to one estimate Kalinga had an army with 60,000 infantry, 1000 cavalry and 700 elephants.  The existence of such a big army in the neighbourhood provoked Ashoka to attack Kalinga.

The material prosperity of Kalinga could be another reason which drew the attention of Ashoka. Kalinga was very rich and wealthy at that time. It was a navigational giant with commercial relations with far off countries like Cylone, Sumatra, Java, Malaya and others. Its prosperity was augmented by its foreign trade. Ashoka might have been attracted by the wealth of Kalinga.

The strategic location of Kalinga could also be a reason for its attack. The occupation of Kalinga could make the south easily accessible for Magadha. Further, Magadha was a land locked state which didn’t have sea route. Ashoka wanted to control the sea routes to south-east Asian countries for which he wanted to occupy Kalinga.

Some historians believe that Ashoka had heard of the breathtaking beauty of Kalingan princess Karuvaki, whom he wanted to marry. As his proposal was turned down by the Kalingan ruler he took the extreme step of plundering Kalinga and Karuvaki in a single stroke. This story seems to be a myth with little historical support.

However there was not a single reason which prompted Ashoka to attack Kalinga. A number of factors might have influenced him to undertake the expedition.

Ashoka had fought a number of wars before he took on Kalinga. Kalinga war was the most difficult and hardest battle Ashoka had ever fought. The carnage, death and deportation which occurred during Kalinga war was incomparable. 1,00,000 men were slain,1,50,000 were deported and many more died. The blue waters of river Daya on the bank of which Kalinga war was fought became red for months. Ashoka had never seen such a violent war ever before. After defeating the Kalingan army, he had to face the commoners. He was taken aback at the heroism and braveness of the common Kalingans.

The conquest of Kalinga was a great landmark in the history of warfare and religion. Ashoka was stricken with remorse after he saw the terrible slaughter of human beings. Being disgusted with war, he ceased to pursue any more war or aggression. In a penitent mood Ashoka bid farewell to the policy of ‘Digvijay’ and adopted the policy of ‘Dharmavijay’. Due to his repentance for the evils of conquest, Ashoka embraced Budhism- the religion of peace, tolerance and nonviolence under the influence of Upagupta- a Kalingan monk. He took the vow of spreading ‘Dharma of Ahimsa’. Ashoka the conqueror got converted into Ashoka the missionary. Instead of ‘Verighosa’ he adopted ‘Dharmaghosa’. Instead of ‘Chandashoka’ he became ‘Dharmashoka’. The Kalinga war marked the beginning of an era of peace, tolerance and religious propaganda.

Ashoka undertook Dharmayatras immediately after the end of Kalinga-war. He requisitioned the services of his officials for the propagation of ‘Dharma’. He made pilgrimage to the holy places of Buddhism. He established a number of Dharma Stambhas. Philanthropic and benevolent activities form a large part of his missionary policy. Ashoka convoked the third Buddhist council at Pataliputra for the spread of Buddhism. He sent Dharma missions to different countries of western Asia, Egypt, Burma, Cylone, and Malaya and to a number of other countries. He sent his son Mahendra and daughter Sanghamitra to Cylone for the purpose.

Ashoka was solely responsible for the spread of Buddhism as a universally acceptable religion. Kalinga War which changed Ashoka from a man of war to a man of peace is equally responsible for the spread of Buddhism from the corridors of Pataliputra to Nepal, Tibet, China, Mangolia and the Far-east. Kalinga War is thus a landmark in the history of warfare which paved for the spread of peace.