This is a study of military psychiatry in the Second World War. Focusing on the British Army, it recounts how the military came to employ psychiatrists to revise recruitment procedures and to treat psychiatric casualties. The research has shown that psychiatry was a valued specialty and that psychiatrists were given considerable power and independence. For example, psychiatrists reformed personnel selection and placed intelligence testing at the centre of the military selection of personnel. Psychiatrists argued that by eliminating the 'dull and backward' the tests would help improve efficiency, hygiene, discipline and morale, reduce psychiatric casualties and establish that the Army was run in a meritocratic way. However, it is probable that intelligence testing made it less likely that working-class men would receive commissions. Still, the Army had no consistent military doctrine about what the psychiatrists should be aiming for -to return as many psychiatric casualties to combatant duties as was possible or to discharge men who had found it impossible to adapt to military life. In the initial stages of the war, the majority of casualties were treated in civilian hospitals in Britain, where most were discharged. This was partly because the majority were regarded as constitutional neurotics. When psychiatrists treated soldiers near the front line most were retained in some capacity. The decision on whether to evacuate patients was influenced by multiple factors including the patients' military experience and the doctors' commitment to treatment or selection. Back in Britain, service patients were increasingly more likely to be treated in military hospitals such as Northfield -famous for the 'Northfield experiments'. These provided an alternative model of military psychiatry in which psychiatric intervention refocused away from individuals and their histories and onto social relationships, and where the psychiatrists' values were realigned with the military rather than with civilian general medicine.