In December 1805 Lord Aberdeen took his seat as a Tory Scottish representative peer in the House of Lords. In 1808, he was created a Knight of the Thistle. Following the death of his wife from tuberculosis in 1812 he joined the Foreign Service. He was appointed Ambassador Extraordinary and Minister Plenipotentiary to Austria, and signed the Treaty of Töplitz between Britain and Austria in Vienna in October 1813. In the company of the Austrian Emperor, Francis II, he was an observer at the decisive Coalition victory of the Battle of Leipzig in October 1813; he had met Napoleon in his earlier travels. He became one of the central diplomatic figures in European diplomacy at this time, and he was one of the British representatives at the Congress of Châtillon in February 1814, and at the negotiations which led to the Treaty of Paris in May of that year.