Conquests of Harshavardhanareveal that he had followed the policy of Digvijaya. He had ascended the throne of Thanesar in 606 A.D. His ascension to the throne was a period of political turmoil in Pushabhukti House, owing to the sudden death of Rajya Vardhana, elder brother of Harshavardhana, in the hands of Sasanka of Gauda. Harsha's immediate task after his ascension to the throne was to avenge his enemies. Harsha Vardhana had first outlined the plan of "Digvijaya", which he readily pursued. Harsha and his feudatories dreamt to conquer distant lands, though campaign against Sasanka was his immediate target. After the conquest of Bengal and eastern India, Harsha Vardhana's thirst for conquest increased considerably and he devoted himself to the scheme of conquering whole of India and accomplished successful takeovers for a long period of thirty years. The River Narmada was the southern boundary of Harsha's kingdom.

The military campaigns and conquests of Harsha Vardhana can be categorised into several phases - conquest of Bengal and Eastern India, campaign against western India, the Chalukya War and his war with Sindh. On the northern frontier of his kingdom, Harsha came into contact with Kashmir.

Conquest of Bengal and Eastern India by Harshavardhana
The subjugation of Bengal by Harshavardhana was motivated by the idea of taking revenge against Sasanka. He wanted take revenge against him as he had murdered his brother. Harsha and Bhaskara Varman conjointly attacked Sasanka. During his campaign against Sasanka in Bengal, Harshavardhana had occupied Kannauj and had already strengthened his position. According to an inscription from Bengal it is probable that the whole of Bengal passed under the rule of Harsha. The discovery of an inscription from Eastern Bengal dated in the Harsha era proves that the region was under the sway of the Kannauj monarch.

Campaign against Western India
Harsha's campaign against western India though met with initial success, could not hold permanent control over these regions. Later hostility between Harsha and the western kingdoms was culminated by the matrimonial alliance between the Valabhi king and Harsha's daughter.

Chalukya War
Chalukya War of Harsha Vardhana had confined the area of Harsha's sovereignty. Harsha with the aim of becoming the sole lord of India had projected his campaign against the southern kingdom. But he was confronted with the powerful resistance of Chalukya king Pulakesin II of Vatapi. Hence Harsha Vardhana could not extend the limits of his Empire to the south of the Narmada River. The Chalukya war of Harsha Vardhan destined him as the paramount ruler of north, who had no supremacy over the kingdoms of south India.