The spheres of official communication, which include public administration, legal proceedings, legislation, etc., are regulated, in contrast to everyday communication. Activities in each of these spheres are subject to precisely defined, strictly established rules that regulate and legitimize it. The diplomatic language is characterized by a special degree of regulation. “The weight of a word” in international politics is extremely heavy, since the fate of entire states and peoples may depend on successful or unsuccessful communication between diplomats. The strict standardization of the diplomatic language should serve as a kind of deterrent against the growth of tension in international relations. The goal of this study is to identify the degree of susceptibility of the diplomatic correspondence language to transformations in the political crisis context (during wartime). The research material is based on the texts from the Orange book, a collection of diplomatic correspondence between warring countries before the outbreak of the First World War. The application of the contextual analysis method made it possible to determine the vector of changes in the diplomatic correspondence language caused by the political crisis: from restraint, emotionlessness, tact and politeness accepted in the diplomatic sphere to ultimatumness, categoricalness, manifestation of emotions and deviation from the principle of objective reflection of events.