The decline of the Maurya Dynasty was rather rapid after the death of Ashoka/Asoka. One obvious reason for it was the succession of weak kings. Another immediate cause was the partition of the Empire into two. Had not the partition taken place, the Greek invasions could have been held back giving a chance to the Mauryas to re-establish some degree of their previous power.
Regarding the decline much has been written. Haraprasad Sastri contends that the revolt by Pushyamitra was the result of brahminical reaction against the pro-Buddhist policies of Ashoka and pro-Jaina policies of his successors. Basing themselves on this thesis, some maintain the view that brahminical reaction was responsible for the decline because of the following reasons.
All these four points can be easily refuted. Asoka's compassion towards animals was not an overnight decision. Repulsion of animal sacrifices grew over a long period of time. Even Brahmins gave it up by the book Divyavadana, cannot be relied upon since it was during the time of Pushyamitra Sunga that the Sanchi and Barhut stupas were completed. Probably the impression of the persecution of Buddhism was created by Menander's invasion who was a Budhhist. Thridly, the word 'budheva' is misinterpreted because this word is to be taken in the context of some other phrase. Viewed like this, this word has nothing to do with brahminism. Fourthly, the victory of Pushyamitra Sunga clearly shows that the last of the Mauryas was an incompetent ruler since he was overthrown in the very presence of his army, and this had nothing to do with brahminical reaction against Asoka's patronage of Budhism. Moreover, the very fact that a Brahmin was the commander in chief of the Mauryan ruler proves that the Mauryas and the Brahmins were on good terms.
After all, the distinction between Hinduism and Buddhism in India was purely sectarian and never more than the difference between saivism and vaishnavism. The exclusiveness of religious doctrines is a Semitic conception, which was unknown to India for a long time. Buddha himself was looked upon in his lifetime and afterwards as a Hindu saint and avatar and his followers were but another sect in the great Aryan tradition. Ashoka was a Buddhist in the same way as Harsha was a Budhist, or Kumarapala was a Jain. But in the view of the people of the day he was a Hindu monarch following one of the recognized sects. His own inscriptions bear ample withness to the fact. While his doctrines follow themiddle path, his gifts are to the brahmibns, sramansa (Buddhist priests) and others equally. His own name of adoption is Devanam Priya, the beloved of the gods. Which gods? Surely the gods of the Aryan religion. Buddhism had no gods of its own. The idea that Ashoka was a kind of Buddhist Constantine declearing himself against paganism is a complete misreading of India conditions. Asoka was a kind or Buddhist Constantine declearing himself against paganism is a complete misreading of India conditions. Asoka was essentially a Hindu, as indeed was the founder of the sect to which he belonged.
Raychaudhury too rebuts the arguments of Sastri. The empire had shrunk considerably and there was no revolution. Killing the Mauryan King while he was reviewing the army points to a palace coup detat not a revolution. The organization were ready to accept any one who could promise a more efficient organisation. Also if Pushyamitra was really a representative of brahminical reaction he neighbouting kings would have definitely given him assistance.
The argument that the empire became effete because of Asokan policies is also very thin. All the evidence suggests that Asoka was a stern monarch although his reign witnessed only a single campaign. He was shrewd enough in retaining Kalinga although he expressed his remorse. Well he was wordly-wise to enslave and-and-half lakh sudras of Kalinga and bring them to the Magadha region to cut forests and cultivate land. More than this his tours of the empire were not only meant for the sake of piety but also for keeping an eye on the centrifugal tendencies of the empire. Which addressing the tribal people Asoka expressed his willingness to for given. More draconian was Ashoka's message to the forest tribes who were warned of the power which he possessed. This view of Raychoudhury on the pacifism of the State cannot be substantiated.
Apart from these two major writers there is a third view as expressed by kosambi. He based his arguments that unnccessary measures were taken up to increase tax and the punch-marked coins of the period show evidence of debasement. This contention too cannot be up held. It is quite possible that debased coins began to circulate during the period of the later Mauryas. On the other hand the debasement may also indicate that there was an increased demand for silver in relation to goods leading to the silver content of the coins being reduced. More important point is the fact that the material remains of the post-Asokan era do not suggest any pressure on the economy. Instead the economy prospered as shown by archaeological evidence at Hastinapura and Sisupalqarh. The reign of Asoka was an asset to the economy. The unification of the country under single efficient administration the organization and increase in communications meant the development of trade as well as an opening of many new commercial interest. In the post - Asokan period surplus wealth was used by the rising commercial classes to decorate religious buildings. The sculpture at Barhut and Sanchi and the Deccan caves was the contribution of this new bourgeoisie.
Still another view regarding of the decline of Mauryas was that the coup of Pushyamitra was a peoples' revolt against Mauryans oppression and a rejection of the Maurya adoption of foreign ideas, as far interest in Mauryan Art.
This argument is based on the view that Sunga art (Sculpture at Barhut and Sanchi) is more earthy and in the folk tradition that Maruyan art. This is more stretching the argument too far. The character of Sunga art changed because it served a different purpose and its donors belonged to different social classes. Also, Sunga art conformed more to the folk traditions because Buddhism itself had incorporated large elements of popular cults and because the donors of this art, many of whom may have been artisans, were culturally more in the mainstream of folk tradition.
One more reasoning to support the popular revolt theory is based on Asoka's ban on the samajas. Asoka did ban festive meetings and discouraged eating of meat. These too might have entagonised the population but it is doubtful whether these prohibitions were strictly enforced. The above argument (people's revolt) also means that Asoka's policy was continued by his successors also, an assumption not confirmed by historical data. Further more, it is unlikely that there was sufficient national consciousness among the varied people of the Mauryan empire. It is also argued by these theorists that Asokan policy in all its details was continued by the later Mauryas, which is not a historical fact.
Still another argument that is advanced in favour of the idea of revolt against the Mauryas is that the land tax under the Mauryas was one-quarter, which was very burden some to the cultivator. But historical evidence shows something else. The land tax varied from region to region according to the fertility of the soil and the availability of water. The figure of one quarter stated by Magasthenes probably referred only to the fertile and well-watered regions around Pataliputra.
Thus the decline of the Mauryan empire cannot be satisfactorily explained by referring to Military inactivity, Brahmin resentment, popular uprising or economic pressure. The causes of the decline were more fundamental. The organization of administration and the concept of the State were such that they could be sustained by only by kings of considerably personal ability. After the death of Asoka there was definitely a weakening at the center particularly after the division of the empire, which inevitably led to the breaking of provinces from the Mauryan rule.
Also, it should be borne in mind that all the officials owed their loyalty to the king and not to the State. This meant that a change of king could result in change of officials leading to the demoralization of the officers. Mauryas had no system of ensuring the continuation of well-planned bureaucracy.
The next important weakness of the Mauryan Empire was its extreme centralization and the virtual monopoly of all powers by the king. There was a total absence of any advisory institution representing public opinion. That is why the Mauryas depended greatly on the espionage system. Added to this lack of representative institutions there was no distinction between the executive and the judiciary of the government. An incapable king may use the officers either for purposes of oppression or fail to use it for good purpose. And as the successors of Asoka happened to be weak, the empire inevitably declined.
Added to these two factors, there is no conception of national unity of political consciousness. It is clear from the fact that even the resistance against the greeks as the hated miecchas was not an organized one. The only resistance was that of the local rulers who were afraid of losing their newly acquired territory. It is significant that when Porus was fighting Alexander, or when Subhagasena was paying tribute to Antiochus, they were doing so as isolated rulers in the northwest of India. They had no support from Pataliputra, nor are they even mentioned in any Indian sources as offering resistance to the hated Yavanas. Even the heroic Porus, who, enemy though he was, won the admiration of the Greeks, is left unrecorded in Indian sources.
Another associated point of great importance is the fact that the Mauryan Empire which was highly centralized and autocratic was the first and last one of its kind. If the Mauryan Empire did not survive for long, it could be because of the failure of the successors of Asoka to hold on to the principles that could make success of such an empire. Further, the Mauryan empire and the philosophy of the empire was not in tune with the spirit of the time because Aryanism and brahminism was very much there. According to the Brahmin or Aryan philosophy, the king was only an upholder of dharma, but never the crucial or architecture factor influencing the whole of life. In other words, the sentiment of the people towards the political factor, that is the State was never established in India. Such being the reality, when the successors of Asoka failed to make use of the institution and the thinking that was needed to make a success of a centralized political authority. The Mauryan Empire declined without anyone's regret.
Other factors of importance that contributed to the decline and lack of national unity were the ownership of land and inequality of economic levels. Land could frequently change hands. Fertility wise the region of the Ganges was more prosperous than northern Deccan. Mauryan administration was not fully tuned to meet the existing disparities in economic activity. Had the southern region been more developed, the empire could have witnessed economic homogeneity.
Also the people of the sub-continent were not of uniform cultural level. The sophisticated cities and the trade centers were a great contrast to the isolated village communities. All these differences naturally led to the economic and political structures being different from region to region. It is also a fact that even the languages spoken were varied. The history of a sub-continent and their casual relationships. The causes of the decline of the Mauryan empire must, in large part, be attributed to top heavy administration where authority was entirely in the hands of a few persons while national consciousness was unknown.