The emperor conferred upon each of the eight English officers who were present the Military Order of Maria Theresa, and King George III knighted them as well.
Butler had been promoted lieutenant in the 11th light dragoons in May 1794, and he was in 1796 gazetted major without purchase in the newly raised 87th Royal Irish Fusiliers regiment.
In 1804, he was promoted lieutenant-colonel, and in 1806 the 87th was ordered to form part of the British invasion force under Sir Samuel Auchmuty attacking Montevideo.
In the attack on Montevideo Butler especially distinguished himself, and also in General Whitelocke's attempt to capture Buenos Aires, where the 87th had 17 officers and 400 men killed and wounded.
In 1810, he was second in command of a force ordered from the Cape to assist Major-general Abercromby in the capture of Mauritius, but the island was already taken when the contingent arrived.