Originally published in 1956, "this book mainly confines itself to Fifth Column work developed by Germans. Naturally I am aware that there were other Fifth Columns which moved forward in the international offensive of national socialism. Hitler found accomplices in every country. The time is not yet ripe, however, to give an accurate description of the activities of those multifarious 'native' Fifth Columns. There are no good monographs extant, reliable archive material is hard to come by, and the social and political diversities of those non-German groups who actively sympathised with national socialism is greater and even more confusing than of the German groups. In this study a unifying element lies in the fact that the activities described originated with Germans, whereas a comparative study of the 'native' Fifth Columns would become a tangle of groups of divergent natures, which would each have to be understood from the special angle of its own social and political environment. "-Louis de Jong, Preface