After years of political tension and ethnic conflict, the countries of the Balkan peninsula (Serbia, Greece, Bulgaria, Montenegro) decided in 1912 to join their forces against the Ottoman Empire that was swayed by internal upheaval. Their aim was to liberate their enslaved fellow patriots and to claim their national interests, mainly as regards the
territories of Macedonia and Thrace. The joint effort between these countries caused the dynamic response of the Ottoman Empire, which proceeded with the immediate reinforcement of the border guards and the redeployment of forces to Macedonia and Thrace.
In turn, the Balkan countries proceeded to full mobilization, with Montenegro declaring war on the Ottoman Empire, known as the First Balkan War. Serbia and Bulgaria joined the war on 4 October, followed by Greece on the next day. During the first days, the Greek forces launched attacks towards Thessaloniki, winning their first important victory in the battle of Sarantaporo. The Serbian army occupied territories around Kossovo, while Bulgaria attacked from the east.
The total number of Allied forces stood at 690.000 men, with the Turkish being 345.000. The war escalated quickly with a series of important battles and with the Balkan countries winning major victories against the Ottomans. The commencement of the war marked a critical turning point in the history of the Balkan peninsula and was the forerunner of major changes in the region, preparing the ground for the geopolitical changes that would follow.
