<P> Ashoka was followed for 50 years by a succession of weaker kings . Brihadratha, the last ruler of the Mauryan dynasty, held territories that had shrunk considerably from the time of emperor Ashoka . Brihadratha was assassinated in 185 BCE during a military parade by the Brahmin general Pushyamitra Shunga, commander - in - chief of his guard, who then took over the throne and established the Shunga dynasty . </P> <P> Buddhist records such as the Ashokavadana write that the assassination of Brihadratha and the rise of the Shunga empire led to a wave of religious persecution for Buddhists, and a resurgence of Hinduism . According to Sir John Marshall, Pushyamitra may have been the main author of the persecutions, although later Shunga kings seem to have been more supportive of Buddhism . Other historians, such as Etienne Lamotte and Romila Thapar, among others, have argued that archaeological evidence in favour of the allegations of persecution of Buddhists are lacking, and that the extent and magnitude of the atrocities have been exaggerated . </P> <P> The fall of the Mauryas left the Khyber Pass unguarded, and a wave of foreign invasion followed . The Greco - Bactrian king, Demetrius, capitalized on the break - up, and he conquered southern Afghanistan and parts of northwestern India around 180 BCE, forming the Indo - Greek Kingdom . The Indo - Greeks would maintain holdings on the trans - Indus region, and make forays into central India, for about a century . Under them, Buddhism flourished, and one of their kings, Menander, became a famous figure of Buddhism; he was to establish a new capital of Sagala, the modern city of Sialkot . However, the extent of their domains and the lengths of their rule are subject to much debate . Numismatic evidence indicates that they retained holdings in the subcontinent right up to the birth of Christ . Although the extent of their successes against indigenous powers such as the Shungas, Satavahanas, and Kalingas are unclear, what is clear is that Scythian tribes, renamed Indo - Scythians, brought about the demise of the Indo - Greeks from around 70 BCE and retained lands in the trans - Indus, the region of Mathura, and Gujarat . </P> <P> The Empire was divided into four provinces, with the imperial capital at Pataliputra . From Ashokan edicts, the names of the four provincial capitals are Tosali (in the east), Ujjain (in the west), Suvarnagiri (in the south), and Taxila (in the north). The head of the provincial administration was the Kumara (royal prince), who governed the provinces as king's representative . The kumara was assisted by Mahamatyas and council of ministers . This organizational structure was reflected at the imperial level with the Emperor and his Mantriparishad (Council of Ministers). </P>

Who invaded south asia and set up a state following the mauryan period