During the pre-war negotiations that had resulted in the establishment of the Balkan League, Serbia and Bulgaria signed a secret agreement on 13 March 1912 which determined their future boundaries, in effect sharing northern Macedonia between them.
Sõjaeelsete läbirääkimiste ajal, mille tulemusel loodi Balkani Liit, sõlmisid Serbia ja Bulgaaria 13. märtsil 1912 salakokkuleppe, mis määras nende tulevased piirid, jagades tegelikult Põhja-Makedoonia omavahel.