In July 1806 his uncle was given a new ship, , and orders to convoy General Samuel Auchmuty and his troops to the Río de la Plata and take over command of the squadron there from Admiral Sir Home Popham on the flagship . James accompanied his uncle and saw the fall of Montevideo to General Auchmuty's forces and the capture of twenty-five warships and more than 10,000 tons of merchant shipping. In August 1807 the Stirlings crossed the South Atlantic for a stay of five months at the Cape of Good Hope and at the end of February 1808 the "Diadem" returned to England via a short period in Rio de Janeiro.