The frontiers of the Principality of Albania had not been set during the Paris Peace Conference in 1919, as they were left for the League to decide; they had not yet been determined by September 1921, creating an unstable situation. Greek troops conducted military operations in the south of Albania. Kingdom of Serbs, Croats and Slovenes (Yugoslav) forces became engaged, after clashes with Albanian tribesmen, in the northern part of the country. The League sent a commission of representatives from various powers to the region. In November 1921, the League decided that the frontiers of Albania should be the same as they had been in 1913, with three minor changes that favoured Yugoslavia. Yugoslav forces withdrew a few weeks later, albeit under protest.