With the outbreak of the Second World War, the CID was immediately absorbed into the War Cabinet as Ismay had planned. In the midst of the turmoil, Ismay was promoted to
major-general, Ismay disagreed with several Allied strategic choices, including the decision to try to stop the German advance in Belgium, but kept his doubts to himself.
Chiefs of Staff Committee In April 1940,
Winston Churchill took control of the Military Co-ordination Committee, charged with overseeing all of the military services. He selected Ismay as his chief staff officer, which also gave Ismay the additional responsibility of serving on the
Chiefs of Staff Committee. On 10 May, after the beginning of the
Battle of France, Chamberlain resigned, and Churchill became both prime minister and minister of defence. Ismay, who later called Churchill "the greatest War Prime Minister in our history", was "thrilled" by this development, and continued to act as Churchill's chief staff officer and military adviser. According to Churchill, the two developed a close "personal and official connection [that] was preserved unbroken and unweakened" throughout the war. As part of this relationship, not long after Churchill became prime minister, he arranged for Ismay to be appointed
Knight Commander of the Order of the Bath in June 1940. From the very moment he became prime minister, Churchill "relied heavily on General Pug Ismay," who provided a crucial bridge to the military establishment. Ismay served as the "principal assistant to Mr. Churchill in his capacity as Minister of Defence", continued to serve as the secretary of the Imperial Defence Chiefs of Staff Committee, and became Deputy Secretary of the War Cabinet. Ismay was crucial to running the war effort, as he was able to effectively link the military and civilian leadership.
Jock Colville, Churchill's private secretary, wrote that Ismay had the "tact, patience, and skill in promoting compromise" needed to keep the war running smoothly." In his role, Ismay handled "nearly all military messages" from Churchill to the Service Chiefs. Ismay also gave Churchill advice on military matters, and often "begged him to be reasonable" when he contemplated foolish actions, believing that Churchill's greatest fault was his "impetuous nature and impatience with opposition."
Allied conferences As Churchill's chief military adviser, Ismay frequently attended wartime conferences and meetings of the
Allies and accompanied other British leaders, such as Foreign Minister
Anthony Eden, on their travels. Ismay's travel to the conferences began in 1941, when he went with
Lord Beaverbrook to the
first Moscow Conference. The Conference was also the first time that Ismay worked closely with the Americans, whom he found "quite congenial." Ismay would continue to work closely with the Americans throughout the remainder of the war, and he accompanied Churchill on his 1942 trip to the United States. Eisenhower thought highly of Ismay, remembering him for his "stalwart support", and noting, "He was one of those men whose great ability condemned him throughout the war to a staff position. Consequently his name may be forgotten; but the contributions he made to the winning of the war were equal to those of many whose names became household words." Not long after Eisenhower arrived, on 16 August 1942, Ismay was promoted to the rank of
lieutenant-general.
1943 conferences ,
Churchill and
Admiral Mountbatten at the
Casablanca Conference In January 1943, Ismay accompanied Churchill to the
Casablanca Conference. Ismay attended nearly all of the proceedings of the Conference, and helped work towards consensus where the Americans and British disagreed on issues. Ismay was also appointed to the committee which wrote the formal report of the conference. After the conference, Ismay visited the American headquarters in
Algiers to meet with Eisenhower, and helped resolve some differences of opinion between Eisenhower and his British colleagues. After Casablanca, Ismay accompanied Churchill to the
third Washington Conference in May 1943. At the conference, Ismay first met the American admiral
William D. Leahy, who is often described as his American counterpart. The two developed a friendly relationship, and Leahy wrote in his memoirs: "General Sir Hastings Ismay became my favorite, perhaps because his position closely paralleled my own". After the Washington Conference came the
Quebec Conference in August 1943. Once again, Ismay attended along with Churchill. The Quebec Conference was the first time that the Allied leaders discussed the full details of
Operation Overlord, so Ismay spent much of his time explaining details of the operation to Churchill and other leaders. During the conference, Ismay also observed that
Dudley Pound "had had a breakdown". He took the information to Churchill who demanded Pound's resignation a week later. Shortly after returning from Quebec, Ismay participated in his next conference, travelling with Anthony Eden to the
Moscow Conference in October and November, where he served as Eden's top military adviser. At the conference, Ismay handled all of the Soviet questions about the planning for Operation Overlord, and met
Joseph Stalin personally for the first time. After the conference, Ismay wrote that he "was optimistic about [sic] post-war relations with Russia", showing his belief that the meeting had gone well. Only four days after returning from the Moscow Conference, Ismay left England again for the
Cairo Conference and
Tehran Conference with Churchill. One major source of conflict at the Cairo Conference was an American proposal to appoint an overall commander for the
strategic bombing of Germany. Ismay and the British were strongly opposed, and Ismay wrote a long paper against the idea, which became the basis of British policy on the subject. At Tehran, Ismay helped to argue the case for Operation Overlord, but immediately after the conference he developed
bronchitis and returned to England by ship, scrapping his other plans for the trip.
1944–1945 In the first several months of 1944, Ismay spent almost all of his time planning for the
Normandy Landings. As part of the planning, Ismay personally coordinated the plans for
Operation Bodyguard and
Operation Fortitude, which were designed to deceive the Germans about the planned Normandy landings. In March,
Duncan Sandys, Churchill's son-in-law, told Ismay that
Basil Liddell Hart, a noted strategist and historian, had somehow discovered the secret plans for the Normandy landings. This development had the potential to compromise the entire operation, so Ismay personally interviewed Liddell Hart, who claimed to have simply "worked it all out for himself" without any access to secret information. After their interview, Ismay directed the matter to the
MI5, who never found evidence of wrongdoing, although it is suspected that Liddell Hart may in fact have received information from military planners. in 1945 On 20 May 1944, less than a month before the Normandy Landings were scheduled to take place, Ismay was promoted to the rank of full
general. After the successful D-Day landings, King
George VI decided to visit the troops in Normandy, and selected Ismay to accompany him on the visit. In September, Ismay accompanied Churchill to the
Second Quebec Conference. Ismay also accompanied Churchill on his visits to
Moscow and
Paris in late 1944. In February 1945, Ismay attended the
Yalta Conference. He found the conference different from the previous ones where "the military element had been the prima donna, occupying the centre of the stage." Instead, at Yalta, political issues took precedence, leaving Ismay and other military advisers "waiting for calls that never came". On
VE Day, Ismay found it "quite impossible to be completely happy about the future," due to the lingering Japanese threat, and the rising threat of the
Soviet Union. Nonetheless, he was happy to be one of only three men to hold the same high government position throughout the war in Europe, along with
Edward Bridges, 1st Baron Bridges and the King. ==Post-war military service==