In April 1918 he was made Ambassador to France, which he remained until 1920. In April 1921 he was sent secretly to Ireland for talks with Éamon de Valera, and it is likely that these talks paved the way for the truce which in turn led to the Anglo-Irish Treaty. He again served as Secretary of State for War under Bonar Law and Stanley Baldwin from 1922 to 1924. Derby was made a CB in 1900, sworn of the Privy Council in 1903, KCVO in 1905 and a GCVO in 1908, Knight of the Garter in 1915, GCB in 1920. He was awarded the Freedom of the City of Manchester in 1934.