The Eastern crisis of 1875-1878 is amongst the most intensively researched subjects in the history of international relations. And yet one act in this long drama has received suprisingly little attention despite having caused a minor sensation at the time. The diplomatic mission of Henry VII Prince Reuss to Constantinople during the Russo-Turkish war of 1877-1878 constitutes a fascinating but largely neglected subplot in the tangled political history of that conflict. Filling this void is therefore overdue. Most of the archival material concerning this important diplomatic episode has been accessible for many decades. And the laborious task of sifting through all of this documentary evidence has proven to be a rewarding one. It has yielded a previously untold story that offers some interesting new insights into the Eastern policy of Otto von Bismarck. Specifically it affords an opportunity to test the validity of Bismarck's famous boast that his ambassadors obeyed his orders 'like soldiers on the parade ground'. The portrait that emerges from the source material is much more nuanced and reveals an era in which family ties and dynastic relationships continued to exert a surprisingly strong influence on the conduct of diplomacy.