sentences:  The debacle of the Sino-Indian War and subsequent government inquiries revealing India's military unpreparedness and mismanagement resulted in the Chief of the Army Staff (COAS) Pran Nath Thapar's resignation on 19 November 1962.On 20 November, Chaudhuri succeeded Thapar as officiating COAS with the acting rank of general.Chaudhuri was officially appointed COAS on 20 February 1963, and was promoted to substantive general on 20 July 1963.