In 1805, on the march to Ulm, he received news of his promotion to major-general and his assignment to a command in Italy under the Archduke Charles of Austria. He thus took part in the failed campaign of Caldiero. Peace provided a short respite, which he spent in studying and teaching the art of war. In 1809 he led a brigade in V Corps during the Battle of Eckmühl. Promoted lieutenant field marshal, he commanded a division in IV Corps at the Battle of Wagram. In 1810 he was created a Commander of the Order of Maria Theresa and became "Inhaber" of the 5th Radetzky Hussars. From 1809 to 1812, as chief of the general staff, he was active in reorganizing the army and its tactical system, but, unable to carry out the reforms he desired owing to the opposition of the Treasury, he resigned his position. In 1813 he was Schwarzenberg's chief of staff and had considerable influence on the councils of the Allied sovereigns and generals. Langenau, the quartermaster-general of the Grand Army, found him an indispensable assistant, and he had a considerable share in planning the Leipzig campaign. He won praise for his tactical skills in the battles of Brienne and Arcis-sur-Aube. He entered Paris with the allied sovereigns in March 1814, and returned with them to the Congress of Vienna, where he appears to have acted as an intermediary between Metternich and Tsar Alexander I of Russia, when the two were not on speaking terms.