During 1912, Greece, Serbia, Bulgaria, and Montenegro joined in a Balkan League against the Ottoman Empire. Fearing a new war in the Balkans, the Ottomans mobilized their armed forces on 14 September and began transferring units to Thrace; the Balkan League responded in kind. On 30 September, the League presented the Ottomans with a list of demands regarding the rights of its Christian population. The Ottoman Empire rebuffed the demands, recalled its ambassadors in Sofia, Belgrade and Athens and expelled the League's negotiators on 4 October. The League declared war against the Ottomans, while Montenegro had already began military operations on 25 September.