On the night of June 16-17, 1913, Tsar Ferdinand ordered the assistant commander-in-chief, Lieutenant General Mihail Savov, to start an offensive of the Bulgarian troops against the Serbian and Greek armies.
After the signing of the London Peace Treaty on May 17, 1913, relations in the victorious coalition worsened.
The treaty ends the war, but does not eliminate the military situation in the Balkans. The reason is the tension that arose between the main players in the winning coalition.
If a year ago Bulgaria succeeded through diplomacy in creating an effective and successful bloc against the Ottoman Empire, then in the months surrounding the preparation of the peace treaty in London, Sofia fell into international isolation.
According to some historians, blinded by military success
Czar Ferdinand ordered on June 16, 1913, our army to attack the until recently allies Greece and Serbia.
He is impatient to await the arbitration of the Tsar of Russia.
On June 17, the 2nd Bulgarian army managed to push back the Greek troops along the Struma river valley and capture Gevgeli, breaking the connection between the Greek and Serbian units. Despite the success, the next day the Bulgarian command received an order to stop the offensive and go on the defensive, due to attempts to resolve the conflict diplomatically.
This gives the opportunity on June 19 for the Greek army to launch a counter-offensive, which forces the Bulgarian units to abandon South Macedonia and retreat north to the Kresna Gorge. On July 4, the Greeks renewed their advance along the Struma River valley and by July 7 managed to push the Bulgarian troops out and establish themselves in the Blagoevgrad area. At the same time, the Eastern Greek group advanced along the Mesta River, captured Gotse Delchev and on July 9 penetrated the Razlog field. There is a danger that the Greeks will head towards Dolna Banya, and through Samokovsko Pole towards Sofia. This forces the Bulgarian command to strengthen the defense in this area, with which it manages to block the enemy.
On June 16, the 4th Bulgarian Army received an order to advance,
after which he crossed the rivers Bregalnica and Zletovska and mastered the approaches of the Sultan tepe peak in the Osogovo mountain, helping to break the ties between the Serbian and Greek troops. And here the offensive is stopped, which the enemy takes advantage of. In the following days, the Serbian units went on a counter-offensive and on June 27 they came in front of the Kaliman position, where they were stopped by the Bulgarian troops. The Fourth Bulgarian Army managed to hold back two Greek divisions that were trying to make direct contact with the Serbs.
At the same time, the remaining Bulgarian troops in the composition of the 1st, 3rd and 5th armies advanced along the border with Serbia from Kyustendilsko to Vidin. Due to the Romanian threat from the north and the need for reinforcements against the Greeks in the Struma River, the Bulgarian command issued an order to stop hostilities and go on the defensive. Encouraged by these Bulgarian actions, the Serbian units went on a counter-offensive and succeeded in capturing Belogradchik, and on July 1, an unsuccessful attempt was made to capture the Vidin fortress as well, recalls the Sofia Regional History Museum.
After the refusal of the Bulgarian government to give up Southern Dobrudja, on June 28 Romania also entered the war, whose troops crossed the border into Dobrudja and forced the Danube River at Oryahovo, Gigen and Nikopol. Without encountering serious resistance from Bulgarian units, the Romanian units reached Pirdop, Zlatitsa and Sofia field, and Dobrich, Balchik and Varna were captured in northeastern Bulgaria.
The Ottoman army also took advantage of the situation and entered the south-eastern territories of Bulgaria, capturing Lüleburgas, Lozengrad and Edirne without resistance. It reached Svilengrad, Lyubimets and Elhovo, where it was stopped by the Bulgarian units transferred to the area.
Under the conditions, the Bulgarian government began to look for a peaceful solution to the conflict, but was refused negotiations. The opponents are determined to continue the hostilities and on July 4, Serbian troops advanced towards Tsarevo Selo, but were stopped at Kalimantsi and Golak Mountain. In the Battle of Kalimans that followed on July 11, they were defeated by the Bulgarian troops.
At the same time, the withdrawal of the 1st Bulgarian Army at the beginning of July allows
the Serbian Timoshka group to occupy, together with the Romanians, all of Northwestern Bulgaria without the city of Vidin,
which was besieged from July 12 to 18. For their part, the Greek troops took control of the valley of the Mesta River, the Kresnen gorge and Predela. Despite the Romanian government's invitation to convene a peace conference in Bucharest, to which the Bulgarian government responded, the Greek king Constantine I did not stop the offensive. On July 13 and 14, Simitli and Dedeagach were captured.
Given the circumstances, the Bulgarian command decided on a decisive counteroffensive towards the valley of the Struma River. The attack included the inner flanks of the 2nd and 4th armies, as well as the Samokov and Rhodope detachments. The counteroffensive began on July 15 with the capture of Biyaztepe Heights and a successful attack at Predella, in which the Greek army was threatened with encirclement.
Despite the enemy's resistance, the Bulgarian units managed to cut off the withdrawal routes of the Greek troops through Pehchevo-Strumitsa and Predela-Kresna-Valley of the Struma River. Under the circumstances, the Greek government concluded an armistice with Bulgaria, which came into force on July 18, 1913.
Peace negotiations between Bulgaria, its former allies and Romania last 10 days.
On July 28, 1913, the Bucharest Peace Treaty was concluded in the Romanian capital,
according to which Bulgaria cedes Southern Dobrudja to Romania, and the borders with Serbia and Greece are changed in favor of Bulgaria's neighbors.
On September 16, the Bulgarian government also signed the Constantinople Peace Treaty with the Ottoman Empire, according to which Bulgaria retained White Sea Thrace, but ceded Edirne, Lozengrad, Bunarhisar and Lüleburgas to the Ottoman Empire.
This is the first national disaster.