On October 14, 1915, the Kingdom of Bulgaria declares war on the Kingdom of Serbia and joins World War I on the side of the Central Powers.
At the outbreak of World War I a year earlier, Bulgaria declared that it would remain neutral, but “with guns at its feet“. Both military blocs tried to attract it to their side because of its important strategic location, archives.bg notes.
In May 1915, the Entente promised Bulgaria, in return for its immediate intervention on its part, to receive after the end of the war Eastern Thrace up to the Midia line – Enos, the “undisputed” and part of the “disputed” zone in Macedonia, as well as support in negotiations with Romania for Southern Dobrudja and a cash loan. The proposals were not coordinated in advance with Serbia and Greece, which were categorically against the cession of their territory. At the same time, Germany and Austria-Hungary guaranteed the settlement of the Bulgarians in Southern Serbia (Pomerania) and throughout Serbian Macedonia immediately after their conquest, immediate negotiations with Turkey for territorial concessions, as well as the return of the Bulgarian territories taken under the Treaty of Bucharest, if Greece and Serbia joined the opposing bloc.
Despite the opposition's protest, the Bulgarian government sided with the Central Powers. On August 24/September 6, 1915, it concluded a treaty and a secret convention with Germany, supplemented by a Military Convention with Germany and Austria-Hungary. With them, Bulgaria undertook to join the war on their side, in exchange for receiving the lands taken from the neighboring Balkan countries after the Inter-Allied War and a loan of 200 million francs. On the same date, a convention was signed with Turkey, regulating the correction of the border in favor of Bulgaria along the lower reaches of the Maritsa River.
On September 10/23, 1915, Bulgaria carried out a general mobilization, and on October 1/14, it declared war on Serbia. The First and Second Armies advanced against it, while the Third Army was left in Northern Bulgaria against a possible threat from Romania. At the beginning of the war, the Bulgarian army numbered 530,000 soldiers and officers, but by its end it reached 850,000.
The Bulgarian troops managed to break the resistance of the Serbian and the Entente units that came to their aid. Timoshko, Pomoravije and Macedonia were liberated. The Serbian armed forces were completely defeated. By order of the German military command, the offensive was stopped at the Greek border, which subsequently allowed the Entente to open a second front against the Central Powers. In the liberated territories, the Moravian and Macedonian military inspection districts were established and their administrative arrangement began in accordance with Bulgarian legislation. Later, a third military inspection district was formed in the Aegean Sea.
In 1916, a balance of power was established between the warring groups and positional (trench) warfare was imposed on both the Western and Southern Fronts.
The situation continued for the next two years.
In 1918, Bulgaria and its allies fell into a difficult economic situation. A serious stagnation occurs in the economic life of Bulgaria, the maintenance of the huge army is unbearable for the country.
The essential goods disappear, the black market and speculation are rampant. Hunger riots break out in a number of places, followed by the so-called women's riots.
The enemy makes a breakthrough in Dobro Pole. This causes the outbreak of the Soldiers' Uprising. It is suppressed. However, Bulgaria is forced on September 29 to sign an armistice in Thessaloniki, with which it exits the First World War. The armistice provides for the withdrawal of Bulgarian troops from the territory of Serbia and Greece; immediate demobilization, surrender as prisoners of war to the Bulgarian troops located west of Skopje.
Tsar Ferdinand I was forced to abdicate in favor of his son, Prince Boris of Tarnovski.
The territorial and economic consequences for Bulgaria of the war were catastrophic. By virtue of the Treaty of Neuilly signed on November 27, 1919, it lost Vardar Macedonia along with the Strumica region, which passed into the borders of the Serbo-Croatian-Slovenian Kingdom. Romania received all of Dobrudja. The Aegean Sea was initially placed under the rule of the Entente, but later passed into the borders of Greece. Eastern Thrace remained part of Turkey. The treaty took away Bulgaria's sovereign right to maintain its own armed forces, and colossal reparations of 2.25 billion gold francs were imposed on it.
In addition to the more than 100,000 soldiers and officers killed and missing on the battlefields, tens of thousands were wounded and captured. The country was completely destroyed economically. Bulgaria experienced a second national catastrophe, which also put a tragic end to the national ideal.