 His left flank was secured by Colonel Walter Bourk and in position in the Aughrim Castle ruin, and also guarded by the cavalry regiments of the Earl of Lucan, Brigadier Henry Luttrell and Colonel John Parker, and Colonel Purcell's Dragoon Regiment near the castle, all under the command of Major-General Dominick Sheldon.His command was subsequently weakened during the course of battle through transfer of elements of his cavalry and dragoons to the right flank.Purcell's dragoons evidently fought piecemeal, some trooper on the left flank and some on the right flank, mounted or dismounted, depending on the situation.