Background
It is gathered from some Puranic descriptions as well as from the famous work ‘Harsha Charita’, written by Bana several centuries later, that the last King of the Maurya Dynasty named Brihadratha was killed by his own General named Pushyamitra Sunga in about 185 or 186 B.C.
With that incident, Pushyamitra captured the throne of Magadha and founded a new dynasty known as the Sunga Dynasty.
The Puranas mention that Pushyamitra Sunga ruled in Pataliputra for 36 years. According to historical calculations, his death took place in around 150 B.C., after which his son Agnimitra succeeded the throne of Sunga Empire.
Pushyamitra Sunga
Pushyamitra was not a great king like any one of the first three Maurya emperors. Compared with them, he appears as an insignificant ruler. His kingdom was too small in size. His capital Pataliputra was also not a strong seat of government as in the days of Chandragupta, Bindusara and Ashoka.
In the wider context of historical continuity, thus, the Sunga rule is noteworthy for maintaining law and order in the Magadhan Kingdom, even though for a brief period.
The former glory of Magadha was no longer there when Pushyamitra Sunga occupied the throne of Pataliputra. The size of the kingdom stood much reduced. Even that reduced territory was not secured. Exactly at the time when Pushyamitra killed the last Maurya Emperor, the territory of Vidarbha proclaimed independence and separated itself from the Magadhan territory. The now king, therefore, declared was against Vidarbha.
In brief, Pushyamitra Sunga maintained his authority over the territory which he inherited from the last Maurya monarch. Even though he was not an aggressive King to extend his kingdom, yet the Sunga Empire was spread over a large portion of the Ganges valley and Northern India.
For achieving victory over Vidarbha and for his successes in driving out the foreign invaders, Pushyamitra demonstrated his glory by performing Ashwamedha Yagna.
King Agnimitra Sunga
The founder of the Sunga Dynasty Pushyamitra was after all a regicide. He might have saved the dying kingdom of Magadha for some time, but his kingship suffered from criticisms. He was described as a pro-Brahamanic and anti-Buddhist king by some critics. His son and successor Agnimitra, however, came to the throne as a legitimate king. Furthermore, he proved himself as an able and benevolent ruler.
When Agnimitra was the Crown Prince, he showed his administrative capability as the governor of the Vidisha region. When Magadha had to fight against Vidarbha, it was Agnimitra who led the Sunga army as its supreme commander against the enemies. By virtue of his courage and heroism, he won the battles for Sunga Empire. It was for him that Vidarbha became a part of the Sunga Kingdom. His heroic deeds seem to have made him a legendary figure, so much so that the celebrated poet of the Gupta golden Age, Kalidasa, wrote his famous historical drama `Malavikagnimitram’, depicting therein Prince Agnimitra as the hero of the drama.
Some coins of Agnimitra’s reign have come to light. But they do not provide any indication about his personality or rule, unlike the Gupta coins of the later times. It is rather tragic that this King ruled only for eight years, as is ascertained from some historical evidences.
King Vasumitra Sunga
Darkness descended on the reigns of the successors of Agnimitra Sunga. It is presumed that his son Vasumitra came to the throne after the death of his father. About this King, only this much is known that as a grandson of Pushyamitra, while a very young prince, he led the Sunga armies against the foreign Yavana invaders and defeated them in battles.
Fall of Sunga Dynasty
Nothing is known about the successors of Vasumitra. But one fact is certain that there was a King named Brihaspati Mitra who ruled over Magadha when Kharavela led his armies to invade the north. According to the Puranic sources, the Sunga rule in Pataliputra lasted for a period of 112 years. The last king of Sunga Dynasty Devabhuti was driven out from the throne by his minister Vasudeva who established a new ruling dynasty known as the Kanva Dynasty.