This thesis is a survey of the available material on the submarine issue during 1914-1917 as a factor in German-American relations which contributed to the American declaration of war in April 1917. No other scholarly work is devoted solely to the submarine issue during this period. The purpose of this thesis is to focus on the submarine as an international legal issue. German-American relations were strained during 1914-1917, because of the different interpretations of international law regarding the submarine. And this thesis was written in order to test the existing historical interpretations of the submarine issue as a focal point of German-American relations.