The founder and the real hero of the dynasty was Pushyamitra Shunga he was the commander-in- chief of the Mauryan army during the reign of king Brihadratha. Pushyamitra assassinated him to become the king himself.
His family had held the viceroyship at Ujjain or the neighbouring province of Vidisa under the Mauryas. His two military achievements were the repulsing of the Greeks twice and conquest over Vidarbha (which Kalidas credits to Agnimitra).
The Testimony of his victories over the Greeks comes from the Gargi Samhita and Malavikagnimitram. The first attack of the Greeks was under Demetrius and the second one under Menander. Pushyamitra had to contend with the invasion of Kharavela, the king of Kalinga, as well. The Shunga kingdom at the beginning comprised the entire Ganges Valley, parts of northern India and Vidisha.
The Puranas assign a reign of 36 years to Pushyamitra, who was succeeded by his son Agnimitra, the hero of Kalidasa’s Malavikagnimitram. Agnimitra was succeeded by Sujyestha who in turn was succeeded by his son Vasumitra.
The next king was Vajramitra who was succeeded by Bhagavata. Bhagavata is also sometimes identified with Kasiputra Bhagabhadra of Vidisa in whose court Heliodorus, the ambassador of Antialkidas stayed. Muladeva, another king of this dynasty whose place in the genealogical list cannot be established, has been identified as the king whose coins have been found at Ayodhya.
This king may be regarded as a predecessor of Dhanadeva described as ‘Lord of Kosala’ in the Ayodhya inscription. However, Muladeva and Dhanadeva were perhaps not the rulers belonging to the main Shunga line. Devabhuti was the last Shunga king, who, it is believed on the authority of Banabhatta, fell prey to the conspiracy hatched by his brahmana minister Vasudeva.
The Shunga dynasty came to an end around 75 BC. The Ayodhya inscription of Dhanadeva states that Pushyamitra performed asvamedha sacrifices twice. The first sacrifice was performed immediately after his ascending to the throne and the second, to mark his victory over the Greeks. Thus the Shungas tried to restore a dead vedic rite.