John Carnac joined the army of the East India Company with the rank of captain in 1758, after seeing service with the 39th infantry regiment. Between 1760 and 1761, as Commander-in-Chief, he fought and ultimately defeated the French-supported forces of the Mughal Emperor, Shah Alam II, near Bihar. Made Brigadier-General in 1764, Carnac again assumed the command of the EIC's army, defeating the Marathas in 1765 before handing control back later that year to Robert Clive. From 1776-1779 he was a Member of Council, Bombay, and a member of the Superintending Committee on the expedition against Poona in 1778. He was dismissed from the EIC for his share in the Treaty of Wadgaon in 1779, under the terms of which the Company relinquished control over all lands gained during the previous four years. Despite this Carnac remained in India until his death at Mangalore in November 1800. The present collection, now held at the National Library of Wales, Aberystwyth, comprises some 2,000 items of correspondence focusing on the earlier period of Carnac's life in India, from 1760 to 1767. This was a period of major political change, with a succession of four different nawabs in Bengal and a change of Mughal Emperor in Delhi. Including a small number of letters in Persian, its emphasis on the years between 1763 and 1766 helps to fill the gap in coverage of events occurring during Clive's absence from India between March 1760 and April 1765. At the same time, the letters serve to amplify our understanding of Clive's third and final tour of duty, by providing the opportunity to contrast how two senior British figures set about implementing the East India Company's new approach, combining commercial interests in Bengal with its growing political power.