Essex set out from Dublin on 9 May to muster his army in the champion fields of Kildare, the Curragh. He marched south, taking the castle of Athy, and was harried by the O'Mores as he passed beyond the Pale. He relieved the fort of Maryborough, and the first significant engagement came in the second week of May at the pass of Cashel in Queens County. The pass was wooded and boggy, with a plashed trench at either end. At the head of his advance were 40 shot and 20 swordsmen. In the face of rebel resistance the calivermen moved to point blank range and the swordsmen jumped into the trenches on the flanks; the vanguard moved through the calivermen in a frontal assault and pressed through to open country, where they halted until the whole column had joined them. Essex was said to have flown like lightning between the vanguard, battle, and rearguard. The English admitted to the loss of three officers and several men although the Irish claimed 500 were killed. The rebels captured many feathered helmets, and the battle became known as The Pass of the Plumes. According to Geoffrey Keating's History of Ireland, "in the year 1599, (Owney Mac Rory Óg O'More) cut off a great number of the troops of the Earl of Essex, in a defile in their progress through Leinster, at a place called from that circumstance "Bearna-Cleitigh", signifying the "Pass of Plumes", from the great quantity of plumes left there, which were worn in the helmets of the English knights who were slain."