They were the two most prominent military figures in the fight to free Europe from the grip of Nazism. But General Dwight D. Eisenhower believed his English comrade-in-arms, General Bernard Law Montgomery, was “a psychopath”. And Monty considered his American counterpart, Ike, “a very, very bad” field commander.

For more than 60 years historians have debated the bitter rivalry that smouldered between the men, but now the sheer depth of their enmity has been revealed in documents from the archive of Cornelius Ryan, an Irish-American war correspondent.

Ryan’s experiences during the liberation of Europe inspired him to write The Longest Day — an account of D-Day that became an international bestseller — and then The Last Battle, a record of the fall of Berlin. The books were built around interviews with soldiers, including the two most prominent Allied military commanders of the war.

In the Eisenhower transcript, recorded in 1963, Ryan gently mentioned Montgomery’s name during a discussion of tactics. Eisenhower snapped, and went into an almost incoherent rage. “First of all he’s a psychopath,” he said. “Don’t forget that. He is such an egocentric that the man — everything he has ever done is perfect — has never made a mistake in his life and on top of that he is just a . . . His memory is bad, very bad, but he thinks it’s perfect, so I don’t . . . He even says that all of the tactical operations after we landed from D-Day went absolutely according to plan!” he said.

Relations between the two began badly when, on their first meeting in 1942, the Englishman ticked off the American for smoking. At a personal level, the men never recovered. At a professional level, their careers had followed radically different paths. Montgomery was a veteran of the First World War and had led the Eighth Army to victory over the Nazi forces at El Alamein. His hard-fought campaigns in North Africa and Italy gave British troops a first taste of victory.

By contrast, Eisenhower was a political animal who had never commanded in the field. “Nice chap, no soldier,” Montgomery remarked. To the arrogant Englishman — “In defeat, unbeatable; in victory, unbearable” Churchill once said — it was only natural that he was appointed to command Overlord. But to contemporary observers it was inconceivable that a British commander would lead a predominantly American army on land.

The tensions emerge in Ryan’s interview with Montgomery in 1963, delivered in the clipped, staccato style of the military man: “History will record that Eisenhower was a very good supreme commander, but as a field commander very, very bad,” he said. “He had no experience for the job. Saw that right from the beginning.”

The transcripts, which are held at the University of Ohio, are unveiled in an exhibition at the University of Edinburgh, which will host a conference on war journalism over Remembrance weekend.

Two of a kind

Dwight D Eisenhower

— Born Texas 1890

— Graduated West Point 1915

— Commanded the Allied Forces landing in North Africa in November 1942

— On D-Day, 1944, he was Supreme Commander of the troops invading France

— Became President of Columbia University after the war

— Ran for President in 1952 and won a sweeping victory with the slogan ‘I like Ike’

Bernard Law Montgomery

— Born London Nov 1887

— Graduated Sandhurst Military Academy 1908

— Served First World War as a captain, seriously wounded when shot in the chest

— Appointed commander of the British Eighth Army in Africa during Second World War

— Served under Eisenhower from December 1943 to August 1944, when he was promoted to field marshal in command of British and Canadian troops

— Created viscount in 1946 and made chief of the imperial general staff

Sources: www.whitehouse.gov , www.euronet.nl

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