Mir Jafar was installed as the Nawab of Bengal by the British East India Company in June 1757 immediately following the Battle of Plassey on June 23, 1757. This victory was achieved through Mir Jafar's betrayal of Siraj-ud-Daulah, the ruling Nawab. Mir Jafar became a puppet ruler under British control, marking the beginning of effective British political dominance over Bengal, which eventually led to the colonization of all of India.