The map embracing the area between south Bulgaria, Greece and Turkey was made in 1923 in the time of establishment of the Republic of Turkey, with Atatürk as its first president, and showcases three different borders between Bulgaria and Turkey. The red line marks Turkey’s current border, the red lined areas are Ottoman borders after the First Balkan War in 1913 and the crosses mark the border between Bulgaria and the Ottomans after the Treaty of Constantinople after the Second Balkan War the same year
In 1912, the Balkan League, formed by the kingdoms of Bulgaria, Serbia, Greece and Montenegro joined against the Ottoman Empire, starting the First Balkan War, which led to the creation of an independent Albania. The Balkan League succeeded in driving out the Ottoman Empire from its European provinces, leaving the Empire with only the Çatalca and Gallipoli peninsulas (here marked with red lines).
In 1913 the Second Balkan war followed, when Bulgaria attacked its old allies Serbia and Greece. The Ottoman Empire used the situation to regain some of the old territories. At the Treaty of Constantinople on 29 September 1913 after the Second Balkan War new borderlines were established.