A forlorn hope was formed by a small detachment of the 54th Foot. This was followed by the combined, elite light infantry and grenadier companies of the regiments involved, as well as the 95th. Next in line were the 38th Foot, followed by the 40th Foot. Two cavalry detachments, from the 17th Light Dragoons and 20th Light Dragoons and 21st Light Dragoons, formed the reserve and rearguard, together with the 47th Regiment of Foot and a small detachment of recruits for the 71st Regiment of Foot (later the Highland Light Infantry). A detachment of Royal Marines was also present. Reinforcements for the defenders came en route from Buenos Aires, so that the rapid success of the operation was essential.