His warning went unheeded, and the Nawab attacked; he captured Fort William which led to the killings of several East India company officials in the Black Hole of Calcutta.[35] A force of Company soldiers (sepoys) and British troops led by Robert Clive recaptured the city the following year.[35] Per the 1765 Treaty of Allahabad following the battle of Buxar, East India company was appointed imperial tax collector of the Mughal emperor in the province of Bengal, Bihar and Orissa, while Mughal-appointed Nawabs continued to rule the province.[36] Declared a presidency city, Calcutta became the headquarters of the East India Company by 1773.[37]