Prasenjit, son of Mahakosala, ruled over the kingdoms of Kashi and Kosala during the 6th century BC with Sravasti as his capital. The kingdom of Kosala was bounded by the Nepal Hills, Panchala, and the rivers Gandaki and Sai.
After the annexation of Kashi, Kosala became a powerful kingdom with suzerainty over the Kalmas of Kesaputta and Sakyas of Kapilavastu.
Prasenjit fought continuously with Ajatashatru, king of Magadha. Prasenjit hated Ajatashatru for murdering Prasenjit’s brother-in-law Bimbisara. His sister, Kosala Devi, had died of grief. Prasenjit revoked the bridal gift of a rich village named Kosaladevi in Kashi. This led to an outbreak of hostilities between Kosala and Magadha, which continued for a long time.
At first Ajatashatru had the upper hand and even drove Prasenjit to Sravasti. In the end, Ajatashatru was entrapped and had to surrender his entire army. Peace was concluded and Prasenjit restored the army, liberty and the disputed village in Kashi to Ajatashatru and also gave his daughter, Vajiri, in marriage to him.
Prasenjit was a contemporary of Buddha, for whom he had great admiration. He also respected the Sakya clan in which Buddha was born. When he asked for a bride from the Sakya clan, the Sakya chief cheated him by offering the daughter of a slave. A son, Vidhudaba, was born out of this wedlock. Prasenjit disowned his queen and son on learning about the fraud but took them back on the advice of Buddha. This led to family dissensions, and Vidhudaba usurped the throne. Vidhudaba had the support of the people also, as they disliked the king’s leaning towards Buddhism. The dethroned Prasenjit proceeded to Rajagriha,the Magadhan capital, to seek the help of Ajatashatru, but he died at the gates of Rajagriha.
Despite his immense respect for Buddhism, Prasenjit did not forsake the traditional Vedic religion and observed Vedic sacrificial practices.
Buddhism, whose foundations were laid in Magadha, attained its full development at Sravasti, where Buddha spend his last twenty one rainy season vassas (retreats) and delivered a number of discourses and formulated in a greater part of this disciplinary code. Buddha gained foot hold in Kosala, especially at Sravasti, due to the support of Prasenjit.
King Prasenjit became a devout listener of Buddha’s discourses, while his queen, Mallika, and his two sisters, Soma and Sakula, became lay devotees.