of intermittent fever obliged him to go home in February, and he saw no further service in the Peninsula. He was appointed a groom of the bedchamber on 28 July. At the end of the year he wrote to Wellington to say that it was proposed he should bring out an hussar brigade, and to ask if he could have command of a cavalry division. Wellington replied that he wished to keep all the cavalry in one division under Cotton (Despatches, Supplementary, vii. 165, 549, and viii. 413. Stewart's letter is misdated 1813). Disappointed in this, Stewart determined to resign his appointment as adjutant-general, which he had originally accepted with reluctance. Wellington was not sorry to lose him. He harassed the cavalry, and had vexed Wellington by his free comments on the way in which it was handled, and by the pretensions which he set up as adjutant-general. Wellington believed also that he intrigued against him in the army, and preached that no good was to be done in Spain; and this was the more serious because, as Wellington told Croker in 1826, ‘Castlereagh had a real respect for Charles's understanding, and a high opinion of his good sense and discretion. This seems incomprehensible to us who knew the two men’ (Croker Papers, i. 346; cf. Craufurd, Life of Craufurd, p. 118). In spite of all this, there were no signs of estrangement in their future relations. Wellington habitually wrote to Stewart in terms of affectionate intimacy, and the latter always showed unstinted admiration for Wellington. An obelisk at Wynyard Park, inscribed ‘Wellington, the friend of Londonderry,’ commemorated a visit from the duke in 1827.
Stewart was made a K.B. on 1 Feb. 1813, and received the Portuguese order of the Tower and Sword soon afterwards, and the gold medal with one clasp in the following year, for his services in the Peninsula. Castlereagh had returned to office as foreign secretary in 1812, and on 9 April 1813 Stewart was appointed British minister to the court of Berlin, ‘specially charged with the military superintendence, so far as Great Britain is concerned, of the Prussian and Swedish armies.’ He reached the headquarters of the allies at Dresden on 26 April, and signed the formal treaty of alliance between Great Britain, Russia, and Prussia. He was present at Lützen, and was actively engaged at Bautzen; and he took part in Blücher's brilliant cavalry stroke at Haynau on 26 May. He helped to storm one of the redoubts at Dresden, and was severely wounded at Kulm. At Leipzig (16 Oct.) Blücher gave him the command of his reserve cavalry, and he captured a battery at the head of the Brandenburg hussars.
But it was in bringing pressure upon Bernadotte that he was of most service to the cause of the allies. He at once recognised the prince royal as ‘a highly finished actor’ who was playing a game of his own, and was not inclined ‘to spill Swedish in drawing French blood.’ But by strenuous exertions and very plain speaking he brought him to take some share in the battle of Leipzig; and he prevented the completion of a convention under which Davoust, who was in Hamburg with thirty thousand men, would have been allowed to return to France. At the same time he kept on good terms with Bernadotte, and received from him the Swedish order of the Sword. He also received the order of the Black Eagle, and six months later of the Red Eagle, of Prussia, and the Russian order of St. George (fourth class). The latter was accompanied by a letter from the Emperor Alexander, bearing witness to his indefatigable zeal and to the coolness and valour he had shown in the battlefield. On 20 Nov. he was given the colonelcy of the 25th light dragoons.
During the campaign of 1814 Stewart was at the headquarters of the allies with Castlereagh. He was present at the actions of La Rothière, Fère-Champenoise, and Montmartre, and at the entry into Paris on 31 March. He was promoted lieutenant-general on 4 June, and was raised to the peerage as Baron Stewart on 1 July. He received honorary degrees at Oxford and Cambridge, was sworn of the privy council on 23 July, and made a lord of the bedchamber in August. On the enlargement of the Bath he received the G.C.B., and in 1816 the G.C.H.
On 27 August 1814 he was appointed ambassador at Vienna. He assisted Castlereagh, and afterwards Wellington, in the negotiations of the congress there, and accompanied the allied sovereigns again to Paris after Waterloo. He represented Great Britain at the congress of Troppau in 1820, and that of Laybach in 1821, and was at Verona with Wellington in 1822. Throughout these affairs he was the zealous instrument of Castlereagh's policy. Among his duties at Vienna was the collection of information about the conduct of Queen Caroline, and he went to England in the autumn of 1820 to advise the government about it. He was a lord of the bedchamber to George IV from his accession to April 1827.
By his brother's death, on 12 Aug. 1822, he became Marquis of Londonderry, and when he found that Canning was to take the foreign office he tendered his resigna-