During the War of the Austrian Succession (1740–1748) France challenged the succession of Maria Theresa to the Habsburg Monarchy. Lord Dillon, as he now was, participated in the Battle of Dettingen on 27 June 1743. Being a peer of Ireland, Lord Dillon resigned the colonelcy in favour of his brother James and left France in 1744 as England prepared a law to forbid its citizens to fight for foreign countries. His brother James succeeded him as colonel-proprietor of Dillon's Regiment.