Anyone who has hitherto studied the history of the international labour movement with respect to its actors discovers more often that not that little knowledge can be gained about the relation between personal ties and political decisions. The focus is always on political affairs, and personal relations remained in the background. The author of this volume sets out from the assumption that international social democracy can be understood as a system of overlapping networks of friends and patrons through whom information is exchanged, solidarity is practised and interests are represented. She shows how profoundly the personal and the political were intermingled. On the basis of an analysis of correspondence between selected social democratic actors from Rumania, Russia and Switzerland around 1900 the author identifies the diverse functions of friendship and networks with respect to the history of the labour movement.