Together with Gladwyn Jebb he helped to negotiate the Italian armistice in August 1943, between the fall of Sicily and the Salerno Landings. This caused friction with Eden and the Foreign Office. He was based at Caserta for the rest of the war. He was appointed UK High Commissioner for the Advisory Council for Italy late in 1943. He visited London in October 1943 and again clashed with Eden. Eden appointed Duff Cooper as Representative to the Free French government in Algeria (after the liberation of mainland France, he later continued as Ambassador to France from November 1944) and Noel Charles as Ambassador to Italy to reduce Macmillan's influence. In May 1944 Macmillan infuriated Eden by demanding an early peace treaty with Italy (at that time a pro-Allied regime under Badoglio held some power in the southern, liberated, part of Italy), a move which Churchill favoured. In June 1944 he argued for a British-led thrust up the Ljubljana Gap into Central Europe (Operation "Armpit") instead of the planned diversion of US and Free French forces to the South of France (Operation Dragoon). This proposal impressed Churchill and General Alexander, but did not meet with American approval. Eden sent out Robert Dixon to abolish the job of Resident Minister, there being then no job for Macmillan back in the UK, but he managed to prevent his job being abolished. Churchill visited Italy in August 1944. On 14 September 1944 Macmillan was appointed Chief Commissioner of the Allied Central Commission for Italy (in succession to General Macfarlane). He continued to be British Minister Resident at Allied Headquarters and British political adviser to "Jumbo" Wilson, now Supreme Commander, Mediterranean. On 10 November 1944 he was appointed Acting President of the Allied Commission (the Supreme Commander being President).