William Deakin, the historian and founding warden of St. Antony’s College, Oxford, who died on Saturday at age 91 in Var, France, is well known in America for assisting in the research of many of Churchill’s best books, including his biography of Marlboro and his multivolume history of World War II, for which Churchill won the Nobel Prize for Literature in 1953.

Deakin’s most important contribution was leading the first British military mission to Tito’s headquarters – thereby playing a salient, if enduringly controversial, role in Churchill’s decision to abandon the Royalist Cetniks in favor of the Communist Partisans.

Deakin was serving as a captain in the Yugoslav section of the British secret service (SOE) at Cairo when, in May 1943, he was parachuted onto Tito’s mobile alpine headquarters. His mission was to ascertain communist strength before the dispatch of a full mission under a brigadier.

Hitherto, the Cetniks, commanded by Drazha Mihailovic, who had been appointed minister of war by the government-in-exile, had been the sole recipient of British aid and recognition.

In his campaign memoir “The Embattled Mountain” (1971), Deakin claimed – dubiously, given his insider knowledge – to have embarked upon this exploratory sally with “unsuspecting innocence.”

The enthusiastic patronage that Mihailovic enjoyed from the Foreign Office and SOE headquarters in London appeared to preclude any attempt to shift policy. But Deakin, as Davidson observed, was “like Churchill himself, among those Conservatives who thought that an alliance with the devil far preferable to allowing the Nazis the least advantage.”

Before the war, Deakin had served as Churchill’s research assistant on “Marlborough: His Life And Times.” He was able to use his personal access to the Prime Minister to circumvent the chain of command. When Churchill visited Cairo in January 1943, Deakin shrewdly counseled him not to break completely with the Cetniks, but urged support for all resistance groups, regardless of ideological leaning.

In consequence, Churchill authorized an independent mission to the Partisans without reference to SOE London. Deakin was chosen to head “Operation Typical” – a six-man joint SOE Military Intelligence mission to Partisan headquarters.

He was dropped near Mount Durmitor at the nadir of Partisan fortunes during the German “Fifth Offensive.” Tito’s 20,000-strong band was surrounded by 120,000 Axis troops. They were forced to undertake a hair-raising crossing of the Durmitor range into the relative safety of Eastern Bosnia. Even grizzled veterans of this most brutal of conflicts were favorably impressed with Deakin’s personal courage.

Despite Tito’s initial suspicion that the British mission’s reports might eventually be passed onto its counterpart attached to Mihailovic, a bond was rapidly forged between the two men, who addressed each other in German. When Tito’s band was caught on an exposed mountainside during a low-level German air raid, Deakin managed to push Tito into a foxhole, so saving his life. Both were wounded, and Tito’s German shepherd, Tiger, and a British soldier were killed.

Deakin – who was neither aware that Tito was the secretary-general of the Communist Party, nor of high-level contacts between the Partisans and the Germans – was favorably impressed by the Yugoslav’s “pragmatism.”

Convinced that Tito rejected any sort of postwar revolution, Deakin next concluded that Mihailovic was closely collaborating with the Germans. He extolled the fighting capacities of the Partisans, requesting urgent resupply, and admitted taking on “a binding and absolute identity with those around me.”

Such was the message which Deakin conveyed to Brigadier Fitzroy Maclean who, as doubts mounted about Mihailovic, had been dispatched in September 1943 as Churchill’s personal liaison officer (and into whose mission Deakin’s was subsumed).

Maclean not only accepted Deakin’s estimate of Partisan strength – itself twice the Germans’ own – but tripled it. After Maclean had been secreted out, he returned in November 1943 to collect Deakin by aircraft so that he could report in person to Churchill (who was again in Cairo).

For nearly two hours, Churchill interrogated Deakin. “It was a miserable task,” Deakin recalled. “As I talked, I knew that I was compiling the elements of a hostile brief which would play a decisive part in any future break between Britain and Mihailovic.”

Churchill instructed Deakin personally to convey to King Peter – then also in Cairo – the evidence of his war minister’s collaboration. The King was mortified.

In February 1944, Churchill was able to report to the House of Commons that “a young friend of mine” had completed his mission. Deakin – who by then had become head of SOE Cairo – was decorated and attached to the staff of Harold Macmillan (minister resident in the Mediterranean) as adviser to the Balkan Air Force.

While Deakin was stationed at Bari, the final decision was taken to withdraw the military missions from Mihailovic’s forces. Following the Partisan victory, Deakin moved to the re-established embassy in Belgrade as first secretary and charge d’affaires, where he witnessed Tito’s disregard for his earlier promises.

Such was the atmosphere that, when Deakin received the news of the Conservative defeat in 1945, one old woman commented to him: “Poor Mr. Churchill. I suppose that now he will be shot” – as was Mihailovic in the following year, after his eyes had been gouged out.

Frederick William Dampier Deakin was born on July 3, 1913, and educated at Westminster and Christ Church, Oxford, where he took a First in Modern History. He was elected a Fellow of Wadham College in 1936,and later that year became Churchill’s literary assistant. Deakin adapted swiftly to Churchill’s unorthodox working methods and was soon attending meetings of Churchill’s “wilderness years” coteries. Such was his esteem for Deakin that in 1938, Churchill dispatched him to President Benes of Czechoslovakia to gauge the embattled Republic’s intentions.

When war broke out, Deakin joined the Queen’s Own Oxfordshire Hussars (Churchill’s old regiment). Despite Churchill’s return to the Admiralty, the research on “A History of the English-Speaking Peoples” continued apace. Even during the Norway campaign of April 1940, Deakin was obliged to present himself at 11 p.m. to Admiralty House to discuss the chapters on the Norman Conquest.

In 1941, Deakin transferred to the SOE, and was initially deployed recruiting young Communists of Croatian origin in Canada.

After the war, he resigned from the Foreign Office, and resumed his Wadham Fellowship and his position as Churchill’s director of historical researches. When Churchill began work on his monumental “The Second World War,” Deakin sifted through the mass of papers then held in the Cabinet War Rooms and drafted much of the text.

Deakin then accepted the challenge of becoming the founding warden of St. Antony’s, established in 1949. He was obliged to devote much time to fund-raising, and despite his evident distaste for the task, was notably successful with such charities as the Ford Foundation.

In part, his achievement derived from his “expand to survive” philosophy; he helped to pioneer “regional studies” as part of the International Relations syllabus and Russian, Latin American, and Far Eastern Centers were all established under St. Antony’s aegis.

Notwithstanding the delight he took in writing about conspiracy, Deakin took umbrage at the widespread suggestion that St. Antony’s was a training ground for spies.

Deakin’s books included “The Brutal Friendship” (1962), which analyzed the Hitler-Mussolini alliance, and “The Case of Richard Sorge” (1965), which recounted the life of the Tokyo-based German communist who gave Stalin forewarning of Operation Barbarossa. But despite the critical acclaim that greeted these works, Deakin remained irrevocably associated with the Yugoslav controversy.

In 1954, Evelyn Waugh – for whom Deakin had tried to obtain a temporary consular appointment, to monitor the persecution of his Croatian co-religionists – wrote to Ann Fleming: “Bill Deakin is a very lovable and complicated man. He can’t decide whether to be proud or ashamed of his collaboration with Tito.”

Deakin’s public and personal pronouncements belied such inner turmoil. After Tito’s break with Stalin in 1948, Deakin was an influential exponent of the orthodoxy, best expressed by Ernest Bevin, that “Tito is a scoundrel, but he is our scoundrel.”

Some observers adjudged that the memory of the wartime friendship with Deakin emboldened Tito to breach the Iron Curtain. Moreover, by his teaching gifts, Deakin ensured that future generations of historians would continue to verify his version of events.

In 1967, he was invited to form the British section of the International Committee for the History of the Second World War. Anglo-Yugoslav colloquia, chaired by Deakin, met privately and by invitation only, with the Yugoslavian view represented by official historians.

After his retirement as warden in 1968, Deakin moved to France. He continued to visit Tito on his palatial island retreat at Brioni, and in 1980, he was part of the official British delegation at his funeral.

When faced with a string of “revisionist” histories and the breakup of the Titoist federation, Deakin opted for a dignified silence.

He was knighted in 1975; held the Russian Order of Valor (1944), the Chevalier de la Legion d’Honneur (1953), and the Yugoslav Partisan Star, 1st Class (1969).