His first action after the refusal was to mount a counter-guerrilla expedition into the Wicklow Mountains early in June 1650, to secure his lines of supply for the Siege of Waterford in south-east Ireland. Ireton then blockaded Waterford into surrender by August 1650. Ireton systematically constructed trenches to bring his siege guns within range of the walls and stationed a parliamentary fleet off the city to prevent it being supplied. Thomas Preston surrendered Waterford after a three-month siege. Ireton then advanced to Limerick by October, but had to call off the siege due to cold and bad weather. Early in 1651, Ireton ordered that areas harbouring the guerrillas should be systematically stripped of food – a scorched-earth policy that caused a famine in Ireland by the end of the year. Ireton returned to Limerick in June 1651 and besieged the city for five months until it surrendered in October 1651. At the same time, parliamentarian forces conducted the Siege of Galway, and Ireton rode to inspect the command of Charles Coote, who was blockading that city. The physical strain of his command took hold on Ireton and he fell ill.