The Magadhan Empire which had been roared by the successive wars culminating in the conquest of Kalinga, began to disintegrate after the exit of Ashoka in 232 BC. Several causes seem to have brought about the decline and fall of the Mauryan Empire.
- Brahmanical Reaction: Asoka prohibited the killing of animals and birds, and derided superfluous rituals performed by women. This naturally affected the income of the brahmanas. The anti-sacrifice attitude of Buddhism and of Asoka naturally brought much loss to the brahmanas and they developed some kind of antipathy toward him.
- Some of the new kingdoms, which arose on the ruins of the Maurya empire, were ruled by the brahmanas like the Sungas and the Kanvas. These brahmana dynasties performed the Vedic sacrifices, which were neglected by Asoka.
- Financial Crisis: The enormous expenditure on the army and payment to bureaucracy created a financial crisis for the Mauryan empire.
- Oppressive Rule: In the reign of Bindusara, the citizens of Taxila bitterly complained against the mistrust of wicked bureaucrats (dushtamatya), and their grievances were redressed by the appointment of Asoka. But when Asoka became emperor, a similar complaint was lodged by the same city but he failed to stop the oppression.
- Spread of new material knowledge in outlying areas: The regular use of iron tools and weapons in peripheral provinces coincided with the decline and fall of the Mauryan empire.
- Weak successor: After the death of Ashoka, the Mauryan Empire was ruled by a series of weak and ineffectual rulers. These rulers were not able to maintain the unity and stability of the empire, and as a result, the empire began to disintegrate.
- Neglect of the North-West Frontier and the great wall of China: Around 220 BCE, the Chinese emperor Shih Huang Ti built the Great Wall of China to defend his empire from the nomadic Scythians of central Asia. Emperor Ashoka did not take any such precautions on India’s northern border.
- To flee the Scythians, the Parthians, Shakas, and Greeks were compelled to travel to India. The first invaders to reach India were the Greeks, who founded the kingdom of Bactria in present-day northern Afghanistan in 206 BCE.