ABSTRACT After the Union of South Africa declared war on Germany in September 1939 approximately 5000 German men were interned as ‘enemy aliens'. Fears of a destabilisation of South Africa by German ‘fifth columnists’ were nurtured by the fractured social and political environment of the Union. The attempts made by Afrikaner nationalists to undermine the war effort of the Union reverberated with anti-Semitic and anti-British Nazi propaganda. Apprehensions about the disruptive effects of Nazi activities among Afrikaners and German residents also blended with the perpetual fears of the white minority about losing control of the black population. These challenges to domestic security convinced the Smuts government that the internment of German men suspected of subversion was urgent and justified. The internment of German civilian internees in South Africa has been briefly mentioned in some studies, but this article seeks to provide a more detailed analysis of their internment against the background of wartime South Africa. Based on South African and German archival and secondary sources, this article also constitutes a first attempt at exploring important aspects of the conditions inside the internment camps.