On June 27, 1913, during the Allied War, Romania declares war on Bulgaria. Almost half a million Romanian army crossed the Danube river, and taking advantage of the exposed Bulgarian rear, reached 30 km from Sofia. Days earlier, Greece and Serbia declared war on Bulgaria.
The Inter-Allied War ended with the signing of the Bucharest Peace Treaty on July 28, 1913, according to which Bulgaria was deprived to a significant extent of the lands it had liberated during the Balkan War (1912 – 1913) and suffered heavy financial and other losses, radio "Veliko Tarnovo" reported.
The Inter-Allied War or the Second Balkan War – 1913 was the war between Bulgaria and its former allies from the Balkan Union 1912 – 1913 – Serbia, Greece and Montenegro, and Romania joined them.
After the victory over Turkey in the Balkan War (1912 – 1913),
sharp disagreements erupt between the Balkan allies over the possession of the liberated territories.
Serbia claims the lands west of the Vardar River and raises the issue of revising Bulgarian – the Serbian treaty of 1912 Greece claims the territories of southern Macedonia and part of western Thrace. The claims of the two countries are groundless, as they refer to lands inhabited mainly by the Bulgarian population.
Acknowledging its decisive merit for the defeat of Turkey in the Balkan war, Bulgaria insists on receiving all of Macedonia, emphasizing the fact that the predominant ethnic element in it is Bulgarian.
On May 19, 1913, Serbia and Greece signed a secret military – a political agreement that is directed entirely against Bulgaria. By virtue of this act, all lands to the west and east of the Vardar River to Mount Osogovo are granted to Serbia.
Greece recognizes the lands located south of Mount Belasitsa to Elefthera Bay, which is located east of the mouth of the Struma River.
The two countries undertake to give each other full support in the event that one of them goes to war with Bulgaria. Soon after the signing of this treaty, statements were made from Bucharest that Romania was seeking the friendship of Serbia and Greece.
Under the pretext of not allowing a violation of the “Balkan balance” on the part of Bulgaria,
Romania lays claim to South Dobrudja.
Turkey also makes no secret of its desire to regain the lands west of the Medline – Enos. Each of the Balkan countries began to prepare for war. 600,000 people were mobilized in Bulgaria, but practically 500,000 people could have been used.
Immediately after the conclusion of the London Peace Treaty in 1913, by order of the Bulgarian military command, all Bulgarian troops stationed in the region of Eastern Thrace were transferred to the west for actions against the Serbian and Greek armies. After the hastily prepared plan, military actions were projected only against these two countries, therefore almost no military forces were left on the Turkish and Romanian borders.
Serbia and Greece, which also did not demobilize their armies, have a total of 550,000 men, joined by a Montenegrin division of 12,000 men. After the intervention of Romania and Turkey
A further additional military force of nearly 700,000 men is facing the Bulgarian army.
Despite Bulgaria's extremely unfavorable situation, Tsar Ferdinand I and the royal clique behind him do not hide their intentions for war against Bulgaria's former allies.
Even before June 16, 1913, the Serbian king signed a manifesto declaring war on Bulgaria with an unfilled date.
King Ferdinand I turns out to – unrestrained and on June 16 through his assistant – commander-in-chief gen. M. Savov gives an order for the actions of the Bulgarian army against the armies of Serbia and Greece, which in turn take an offensive against Bulgaria. Montenegro immediately joined their side.
On June 27, Romania also joined the conflict, and 3 days later – late – and Turkey. Faced alone against all its neighbors, despite some successes against the Serbian and Greek armies, Bulgaria was forced to capitulate.
Romania and Turkey are particularly relaxed in their actions against her. Without meeting any resistance,
Romanian troops cross Northern Bulgaria for a few days and end up in Sofia.
The Turkish army manages, also without any opposition from the Bulgarian side, to seize Eastern Thrace.
Austria-Hungary and Germany, which most – greatly encouraged King Ferdinand I for the war, after its outbreak they did not take any steps to deter the actions of the other Balkan states against Bulgaria.
Their desire is to deepen the contradictions in the Balkans as much as possible and to liquidate the Balkan Union. On July 28, 1913, the Bucharest Peace Treaty was signed, according to which Bulgaria was not only deprived to a significant extent of those liberated from it during the Balkan War of 1912. – 1913 lands, but also suffered heavy financial and other losses.
Despite Bulgaria's defeat in the Inter-Allied War, King Ferdinand I managed to stay on the throne.