How did India become united into one empire Who led them?

India became united into one empire primarily under the rule of the Maurya Empire, founded by Chandragupta Maurya in the 4th century BCE. Chandragupta, with the guidance of his advisor Chanakya, successfully unified various regional kingdoms and tribes through military conquest and strategic alliances. This unification was further solidified under his grandson, Ashoka the Great, who expanded the empire and promoted Buddhism, fostering a sense of cultural and political cohesion across the subcontinent.