When war broke out between Italy and Britain in June 1940, long-standing stereotypes of the Italian diasporic population as dirty, servile, and racially inferior were joined by imputations of potentially cowardly and treacherous behaviour. Whilst the internment of first-generation Italian immigrants as the ‘enemy within’ is increasingly integrated into Britain’s wartime narrative, little research has been undertaken on the experiences of second-generation Italians who, as British subjects, faced enlistment in the British Forces. This article addresses the fact that, in the years preceding the outbreak of the Second World War, the British Security Service (MI5) agitated for a ban on the enlistment of dual nationals of Italian or German origin into the armed forces. As well as being prompted by shifting geopolitical circumstances and the presence of ‘subordinate’ organizations established by Italy and Germany in inter-war Britain, this campaign was informed by long-enduring notions of racial difference. Dual nationality, within the racialized perspective of the Security Services, came to be perceived as an obstacle to fully accessing British citizenship, with the question of ‘doubtful parentage’ acting to signify potential disloyalty and duplicity. During the war itself, the War Office initially developed a policy of protection towards recruits of Italian or German origin, which aimed to protect this cohort of soldiers from being shot as ‘traitors’ if captured on active service overseas. Yet, at the same time, MI5 continued to foreground the subversive potential of British Italian soldiers, based upon their racialized notion that dual allegiance would lead to ‘unreliability’ in the field.