The centre of action at that time was in the Punjab, where the Vedas were written. The Rig Veda, written during that period, has a special mention of Prayag as a holy place. The Vatsas, or Vamsas, are called upon to become a branch of the Kurus. The Kurus ruled the Doab and Kurukshetra area from Hastinapur (near present-day Delhi). In the Later Vedic period, when Hastinapur was destroyed by floods, the Kuru King Nichakshu transferred his entire capital with its citizens to a place next to Prayag, which he named Kaushambi (identified with the village Kosam, 56 km away from Prayagraj).
The Vatsa or Vamsa country corresponded with the territory of modern Prayagraj in Uttar Pradesh. It had a monarchical form of government with its capital at Kausambi, now part of Allahabad division .Udayana was the ruler of Vatsa in the 6th century BCE, the time of Buddha. He was very powerful, warlike and fond of hunting. Initially king Udayana was opposed to Buddhism but later became a follower of Buddha and made Buddhism the state religion.