In hot harvest weather, Clifford's force marched from Athlone through Roscommon, Tulsk, and Boyle. At 4pm on 15 August, they reached the foot of the Curlew Mountains (highest point 860 feet), which had to be crossed before Sligo could be approached. The expedition was poorly supplied, and Clifford's men were tired and hungry, and probably in no fit state to continue. But Clifford had received false intelligence that the pass was undefended, and he therefore chose to seize the opportunity and march across, promising his troops plenty of beef in the evening. This meant that his men missed out on the rest that had been planned for them in Boyle, whereas the Irish were well-fed and prepared.