The "Badal Pillar Inscription" depicts that Devapala's Brahmin minister Darbha Pani and the latter's grandson Kedara Mitra were helpful in the expansion of Devapala's kingdom. "Badal Pillar inscription" also depicts how Darbha Pani had used his diplomacy to make Devapala the lord paramount of entire north India. Devapala had conquered the Utkalas, Huns and the Gurjaras. He made significant additions to his father's Empire by conquering the frontier states. He had also conquered the violent tribes Khasas, Latas and had occupied their kingdoms. In the east, kings of Pragjyotishas and Kamarupa became his vassal. In the south, king of Utkala was routed in a battle and the province was overrun by Jaya Pala, brother and general of Devapala. The Orissa king Siva Kara also became his vassal.
Devapala's imperial vision confined to North and South India. Devapala had conquered the Dravidians in South India. Devapala also defeated the Pandya king Sri Mara Sri Vallabha, adversary of Pala king Devapala.
Devapala was also a great patron of literature, education and culture apart from being a great conqueror. During his reign, Bengal had accomplished prosperity in every field. Devapala was a staunch Buddhist and is stated to have granted five villages to Buddhist monasteries for the promotion of Buddhism and welfare & comforts of the Bhiksushs. He is said to have taken initiatives to construct numerous temples and monasteries in Magadha. As an administrator Devapala was very benevolent. He was tolerant towards other religious creeds and promoted growth of other religions within his Empire.
Devapala was practically regarded the most powerful monarch of Northern India during the first half of ninth century. He had rounded off the Pala Empire in the east and southeast (Kamarupa and Utkala) and kept a constant check on further uprising of the Pratihara and Rashtrakuta powers. He led his forces to Vindhyas in the south and the Indus to the west. He was powerful enough to interfere in the politics of the Tamil Nadu join confederacy against the Pandya King. Sailendra king Balaputradeva of Java and Sumatra had sent an envoy to his kingdom by seeking the grant of five villages to build up a monastery in Nalanda. During his reign Nalanda had transformed into the chief seat of Buddhist learning in ancient India. People from different parts of India and even from abroad came to Nalanda University in order to learn Buddhist literature. A galaxy of scholars had flourished during his reign. Bengal had fulfilled unprecedented progress during his reign.
Devapala's victorious record was devoid of defeat. Under his rule Pala domination reached its highest water mark. However Devapala's death led to the decline and disintegration of Pala dynasty.