Based on the most recent publications in the field of the history of international relations and of World War I and using a series of documentary sours hitherto partially or totally ignored by historians, the article examines the relationship between ideology and diplomacy during the first months of the Soviet state's existence. It focuses on the diplomatic conflict between Soviet Russia and Romania which erupted in late 1917 and early 1918. The diplomatic dispute which arose between these two former allies within the Entente bloc has a larger relevance for the study of diplomatic history; particularly for the transition from Tsarist to Bolshevik diplomacy. This case study reveals, interesting patterns in the interaction between different perspectives which co-existed,:at the level of Bolshevik leadership regarding the role of diplomacy in the 'proletarian !state', the mechanisms of constructing its foreign policy, and the principles for interaction with foreign states, viewed, as -ideological enemies This: case study allows the authors to conclude that re-Volutions represent crucial moments leading to profound changes within the stem. of international relations. On the one hand, ; ideological factor has a very significant role in this process. On the other hand, from the point of view of its relations with other states, any successful revolutionary movement Attempts to find a compromise between the strongly ideological revolutionary discourse and certain elements, techniques and Strategies characteristic for traditional diplomacy