Second Balkan War - First Balkan War

First Balkan War

During the First Balkan War, the Balkan League (Bulgaria, Serbia, Montenegro and Greece) succeeded in driving out the Ottoman Empire from its European provinces (Albania, Macedonia, Sandžak and Thrace), leaving the Ottomans with only the Çatalca and Gallipoli peninsulas. The Treaty of London, signed on 30 May 1913, which ended the war, acknowledged the Balkan states' gains west of the Midia-Enos line that was the boundary line between the Ottoman Empire and the allies drawn from Midia (Kıyıköy) to Enos (Enez), on an uti possidetis basis, and created an independent Albania.

However, the relations between the victorious Balkan allies quickly soured over the division of the spoils, especially Macedonia. During the prewar 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. In case of a postwar disagreement, the area to the north of the Kriva Palanka–Ohrid line (with both cities going to the Bulgarians), had been assigned as a "disputed zone" under Russian arbitration and the area to the south of this line had been agreed to become part of Bulgaria. In the event, during the war, the Serbs succeeded in capturing an area far south of the agreed border, down to the Bitola–Gevgelija line (both in Serbian hands). At the same time, the Greeks were able to advance north, occupying Thessaloniki shortly before the Bulgarians arrived, and establishing a common border with Serbia.

When Bulgaria called upon Serbia to honor their prewar agreement over northern Macedonia, the Serbs, displeased at being forced by the Great Powers to evacuate Albania, adamantly refused to give up any more territory. Soon thereafter, minor clashes broke out along the borders of the occupation zones with the Bulgarians against the Serbs and the Greeks. Responding to the perceived Bulgarian threat, Serbia started negotiations with Greece, which also had reasons to be concerned about Bulgarian intentions.

On 19 May/1 June 1913, two days after the Treaty of London was signed and just 28 days before the Bulgarian attack, a secret Serbian-Greek defensive alliance was signed, confirming the current demarcation line between the two occupation zones as their mutual border and concluding an alliance in case of an attack from Bulgaria or Austria-Hungary. With this agreement, Serbia succeeded in making Greece a part of its dispute over northern Macedonia, since Greece had guaranteed Serbia's current (and disputed) occupation zone in Macedonia. In an attempt to halt the Serbo-Greek rapprochement, Bulgarian Prime Minister Geshov signed a protocol with Greece on 21 May agreeing on a permanent demarcation between their respective forces, effectively accepting Greek control over southern Macedonia. However, his later dismissal put an end to the diplomatic targeting of Serbia.

Another point of friction was Bulgaria's refusal to cede the fortress of Silistra to Romania. When Romania after the (First Balkan) war demanded its cession, Bulgaria's foreign minister offered instead some minor border changes, which excluded Silistra, and assurances for the rights of the Kutzovlachs in Macedonia. Romania threatened to occupy Bulgarian territory by force, but a Russian proposal for arbitration prevented hostilities. In the resulting Protocol of St. Petersburg of 8 May 1913, Bulgaria agreed to give Silistra. The resulting agreement was a compromise between the Romanian unsubstantiated demands for Dobrudzha and the Bulgarian refusal to accept any cession of its territory. However the fact that Russia failed to protect the territorial integrity of Bulgaria made the Bulgarians uncertain of the reliability of the expected Russian arbitration of the dispute with Serbia. The Bulgarian behavior had also a long termed consequence over the Russo-Bulgarian relations as together with the uncompromising Bulgarian position tο review the prewar agreement with Serbia during a second Russian initiative for arbitration between them, finally led Russia to cancel its alliance with Bulgaria. Both acts made conflict with Romania and Serbia inevitable.