The paper discusses the drift of the Yugoslav Social Democratic Party towards the Slovene national movement in the year 1918, which the leftist, headed by H. Tuma, oppose, for they see the solution of the national problem in an action of the united European proletariat. In Trieste, the conflicts between the political forces are aggravated when the issue is. raised as to where this nationally mixed territory belongs. The Slovene socialist „youth", as well as the Slovene bourgeois parties, assign it to the future Yugoslavia, the right wing of the Italian socialists, as well as the opposed by the idea of an independent, self-governing Trieste republic, Italian bourgeois parties, assign it to Italy. These two tendencies are advocated by the left wings- in the Slovene and Italian socialist parties with H. Tuma and V. Pittoni. Since the socialists are not ready to carry out this concept in a revolutionary way, at the breakup of Austria-Hungary both parties join the Italian and Slovene bourgeoisie in the committee for national prosperity, with the objective to preserve order and peace. It is only after the Italian occupation that the Slovene and most of the Italian socialists turn towards revolutionary positions.