During 1807-9, Wellington was Chief Secretary for Ireland and a lord of the Treasury.
From July to September 1807, Wellington commanded a division in the expedition against the island of Zealand, and was given command in the Iberian Peninsula in June 1808. In August of that year he won victories at Rolica and Vimeiro, which resulted in the French evacuation of Portugal. After resigning his Irish posts, Wellington was appointed Commander-in-Chief of the British forces in Portugal and marshal general of the Portuguese army. Wellington was to remain in command for six years, during which time he gained notable victories, including Talavera, Busaco, Salamanca and Vittoria; and his services were again employed for the Waterloo campaign of 1815.
In 1809 he was created Viscount Wellington, in February 1812 Earl of Wellington, in October 1812 Marquis of Wellington, and in 1814, Duke of Wellington. He was also to hold the command of the Spanish army for two years from 1812.
From August 1814 to January 1815, Wellington was ambassador extraordinary and plenipotentiary at Paris, and from January to March 1815 was first plenipotentiary to the Congress of Vienna.
Between 1815 and 1818 he was Commander-in-Chief of the allied armies of occupation in France and from August to November 1818 he was joint plenipotentiary to the Congress of Aix-la-Chapelle (WP1/166-612).