Rajendra had demonstrated his military ability by participating in his father’s campaigns. He continued his father’s policy of aggressive conquests and expansion. His important wars were:
1. Mahinda V, the king of Sri Lanka attempted to recover from the Cholas the northern part of Ceylon. Rajendra defeated him and seized the southern Sri Lanka. Thus the whole of Sri Lanka was made part of the Chola Empire. 2. He reasserted the Chola authority over the Chera and Pandya countries.
3. He defeated Jayasimha II, the Western Chalukya king and the river Tungabadhra was recognised as the boundary between the Cholas and Chalukyas.
4. His most famous military enterprise was his expedition to north India. The Chola army crossed the Ganges by defeating a number of rulers on its way. Rajendra defeated Mahipala I of Bengal. To commemorate this successful north-Indian campaign Rajendra founded the city of Gangaikondacholapuram and constructed the famous Rajesvaram temple in that city. He also excavated a large irrigation tank called Cholagangam on the western side of the city.
5. Another famous venture of Rajendra was his naval expedition to Kadaram or Sri Vijaya. It is difficult to pin point the real object of the expedition. Whatever its objects were, the naval expedition was a complete success. A number of places were occupied by Chola forces. But it was only temporary and no permanent annexation of these places was contemplated. He assumed the title Kadaramkondan.
6. Rajendra I had put down all rebellions and kept his empire in tact.
At the death of Rajendra I the extent of the Chola Empire was at its peak. The river Tungabadhra was the northern boundary. The Pandya, Kerala and Mysore regions and also Sri Lanka formed part of the empire. He gave his daughter Ammangadevi to the Vengi Chalukya prince and further continued the matrimonial alliance initiated by his father. Rajendra I assumed a number of titles, the most famous being Mudikondan, Gangaikondan, Kadaram Kondan and Pandita Cholan. Like his father he was also a devout Saiva and built a temple for that god at the new capital Gangaikondacholapuram. He made liberal endowments to this temple and to the Lord Nataraja temple at Chidambaram. He was also tolerant towards the Vaishnava and Buddhist sects.
After Rajendra I, the greatness of the Chola power was preserved by rulers like Kulottunga I and Kulottunga III. Kulottunga I was the grandson of Rajendra I through his daughter Ammangadevi. He succeeded the Chola throne and thus united the Vengi kingdom with the Chola Empire. During his reign Sri Lanka became independent. Subsequently, Vengi and the Mysore region were captured by the western Chalukyas. Kulottunga I sent a large embassy of 72 merchants to China and maintained cordial relations with the kingdom of Sri Vijaya. Under Kulottunga III the central authority became weak. The rise of the feudatories like the Kadavarayas and the emergence of the Pandya power as a challenge to Chola supremacy contributed to the ultimate downfall of the Chola Empire. Rajendra III was the last Chola king who was defeated by Jatavarman Sundarapandya II. The Chola country was absorbed into the Pandya Empire.