“Shattered Communities: Soldiers, Rabbis, and the Ostjuden during Occupation: 1915-1918" addresses the interethnic experience in Poland during the German occupation of 1915-1918. This dissertation demonstrates that the German design for 'modernization' of the East began with the First World War, which envisioned the Jews as a critically vital component, rather than an obstacle to their success. The German military made its connection to the peoples in the East via its own army rabbis and Jewish administrators. This work examines the role of the German Army rabbis, in 1915, in establishing a Jewish press and Jewish schools, along with Jewish relief agencies funded by German Jewish businessmen, in assisting the local Ostjuden communities. By the time the guns stopped firing in 1918, however, the German government had reneged on their promises of recognition and help, and the circumstances of many Ostjuden were as precarious as they had been before the war. Even worse, the experience of war in the East encouraged the rise of racist nationalism in Germany and Eastern Europe. The roots of Nazi policies toward Jews were planted firmly in Poland and Lithuania between 1915 and 1918. But for defeat in the war, it is highly unlikely that the Nazis would ever have risen to power, and in the absence of the German experience of war in the East, the later commitment to a Jewish genocide might never have been imagined. By examining the transnational relationship between the Germans and the Polish Jewish communities during the Great War, I contribute to a better understanding of the complexities leading to the crucial fracture that took place under the pressure of total war in 1917.