It is widely recognized that science played many roles in the Allied efforts during the Second World War, most notably in the atomic bomb project and in the deciphering of the German Enigma code at Bletchley Park. By contrast, little attention has been paid to the wartime activities of psychiatrists and psychoanalysts who were involved in analysing and devising propaganda and in attempting to understand the Nazi mind, as Daniel Pick demonstrates in this fascinating book. Although such psychiatrists and psychoanalysts generally pursued their researches in a secretive manner, they were deemed important to the war effort.

One of the strangest events of the Second World War was the unexpected arrival in Scotland on 10 May 1941 of Rudolf Hess, Hitler's deputy in the Nazi Party and a close confidant of the Führer. Although Hess claimed that his mission was to seek peace with the British government so that Britain and Germany could face their common enemy (Russia), he was incarcerated and later sent for trial at Nuremberg. Although Hess's escapade has been the subject of many books and much conjecture, Pick has examined the attempts by the Allies to understand both him and, more generally, the mentality of the Nazis.

Following his capture, Hess was interrogated for any information that might benefit the British war effort, but subsequently he became an experimental subject for analysts, particular Henry Dicks of the Tavistock Clinic. Ironically he was found to be the antithesis of the physically and mentally superior iron-willed Aryan as depicted in Nazi propaganda. Rather he was found to manifest a cluster of mental problems, including instability, amnesia, hypochondria and paranoid delusions. He claimed that he was being maltreated by his captors and alleged that there were attempts – directed, of course, by the Jews – to poison him. He also adhered to a number of occult beliefs and had arrived in Scotland with quantities of various alternative medical concoctions. Although Hess's doctors declared him to be mentally ill, the evidence they gained was of little practical assistance in the Allied war effort.

While the Hess case provides Pick with a striking case study, his principal concern is the increasing interaction between politics and psychology in the second quarter of the twentieth century and, in particular, the claim that Nazism was not so much a political creed as a mental disease masquerading as politics. Despite the widespread tendency during the 1930s to underestimate the threat from Germany, a number of contemporary commentators perceived Hitler as mentally disturbed and deemed that his illness, as it manifested itself in Nazi ideology, was ultimately responsible for the threat to world peace. Particularly after the 1933 German election and the 1934 Nuremberg Rally, concern was voiced not only about Hitler's mental state but also about his uncanny ability to attract so many Germans to the Nazi cause. How did he achieve such an influence over German society?

A project to analyse Adolf Hitler's mental state and thus to understand his personality, including predictions about how he would pursue the rest of the war, was inaugurated by the Office of Strategic Services (OSS), which was charged with gathering intelligence. Theories about his unstable sexual identity even led some employees of the OSS to propose a scheme to counteract his violent militaristic tendencies by introducing hormones into his diet. More prosaically, Walter Langer, William Murray and other psychiatrists worked on the immense OSS archive – now studied by Pick – containing newspaper reports, transcripts of those who had met Hitler, and other sources, from which they produced detailed psychobiographies of the Führer. Although some of their conclusions were highly speculative, they identified him as sexually perverse, sadistic and utterly convinced of the absolute correctness of his own views. It is ironic that psychoanalysis – which the Nazis had dismissed as a Jewish science while forcing its founder to flee to England – was among the resources used by Dicks, Langer, and others to try to understand the Führer's mind.

Although Pick has focused primarily on British and American interpretations of the Nazi mind, these interpretations by the Allies deserve to be contrasted more extensively with the Nazis' own portrayal of the Aryan mind, both in their propaganda and in the writings of the psychologists who supported the regime. Later chapters concern the post-war period, particularly the Nuremberg Trials (to which many doctors, psychologists and psychoanalysts contributed); Hess's later history; and the Allied attempts to use psychological techniques in the denazification process. Finally, a long chapter on ‘Legacies' addresses how post-war psychologists and sociologists, such as Theodor Adorno, Hannah Arendt and Melanie Klein, drew on the recent history of Nazism in their theorizing about such important issues as hatred, violence and authoritarianism. This large topic perhaps requires a book to itself.