Though the Balkan allies had fought together against the common enemy, that was not enough to overcome their mutual rivalries. In the original document for the Balkans league, Serbia promised Bulgaria most of Macedonia. But before the first war come to an end, Serbia (in violation of the previous agreement) and Greece revealed their plan to keep possession of the territories that their forces had occupied. This act prompted the tsar of Bulgaria to invade his allies. The Second Balkan War broke out on 29 (16) June 1913, when Bulgaria attacked its erstwhile allies in the First Balkan War, Serbia and Greece, while Montenegro and the Ottoman Empire intervened later against Bulgaria, with Romania attacking Bulgaria from the north in violation of a peace treaty.