Second Balkan War: A Detailed Summary

The Second Balkan War was a significant conflict that occurred in 1913 immediately following the events of the First Balkan War.  In fact, the Second Balkan War was a direct result of the First Balkan War, as it saw the former allies of the First Balkan War turn on each other along with other new combatants.  More specifically, the Second Balkan War saw Bulgaria face off against: Greece, Montenegro, Ottoman Empire, Romania and Serbia.

Due to the timeframe in which it occurred, the Second Balkan War (along with the earlier First Balkan War) is considered to be important to World War I.  In fact, historians consider the events of both Balkans Wars to be important causes of World War I, which began in 1914 following the assassination of Austrian Archduke Franz Ferdinand.​

Irredentism

noun

Irredentism is the political goal of uniting people of the same ethnic or national background who live under a foreign government into one country. In the Balkans before World War I, several nations claimed territories controlled by neighbors, which fueled conflicts including the Second Balkan War.

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What Caused the Second Balkan War?

As stated above, the First Balkan War and the tensions present in the Balkans led to the events of the Second Balkan War.  First, the Balkans (along with the rest of Europe) experienced a growth of nationalismA strong pride in one’s country or ethnic group that often drives the desire to expand territory and power. in the 19th century and early 20th century.  This growth in nationalism caused nations within the Balkans to seek to expand their territory and influence in the region.  Ultimately, the growth of nationalism led to the outbreak of the First Balkan War, which was the most direct cause of the Second Balkan War.​

The First Balkan War occurred from 1912 until 1913 and was fought between the Ottoman Empire and the member nations of the Balkan LeagueAn alliance of Bulgaria, Greece, Montenegro, and Serbia that fought together against the Ottoman Empire in the First Balkan War., which included: Bulgaria, Greece, Montenegro and Serbia.  These four nations formed an alliance and took on the Ottoman Empire and its control over southeastern Europe.  At the time, the Ottoman Empire was in a state of decline and struggled to fight back. As a result, the First Balkan War finally ended on May 30th, 1913 with the signing of the Treaty of LondonThe agreement signed on May 30th, 1913 that ended the First Balkan War and transferred Ottoman territory to Balkan League members.. 

With this treaty, the Ottoman Empire gave up large sections of territory in the Balkans, which was taken over by the member nations of the Balkan League.  However, soon after the end of the First Balkan War, Bulgaria expressed frustration with the lands that they received.  This is what ultimately led to the start of the Second Balkan War.​

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In orderHow did the First Balkan War set off a second conflict among the victors?

Follow the chain from top to bottom. Tap any step to read what happened.

1The Balkan League Wins

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2The Treaty of London, May 1913

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3Bulgaria Disputes the Division

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4Serbia Seeks Compensation

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5Bulgaria Attacks, June 29th, 1913

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6The Second Balkan War Begins

The Balkan League WinsIn October 1912, Bulgaria, Serbia, Greece, and Montenegro formed the Balkan League and went to war against the Ottoman Empire. By May 1913, the Ottomans had lost nearly all of their European territory. The four allies now controlled a large block of land but had no agreed plan for dividing it. | swords

The Treaty of London, May 1913The Treaty of London, signed on the 30th of May, 1913, ended the First Balkan War and forced the Ottoman Empire to give up most of its remaining European holdings. The treaty set the outer borders of the new territory but left the division among the Balkan allies unsettled. That unresolved question immediately became a source of conflict between former partners.

Bulgaria Disputes the DivisionBulgaria had fielded the largest army in the war and believed it deserved the biggest share of Macedonia. Serbia and Greece had quietly agreed between themselves to split much of Macedonia, leaving Bulgaria with less than its leaders expected. Bulgarian commanders pressed for a redivision that the other allies refused to accept.

Serbia Seeks CompensationAustria-Hungary had blocked Serbia from gaining an outlet to the Adriatic Sea after the First Balkan War, denying Serbia ports it had hoped to control. Serbia responded by demanding a larger portion of Macedonia to compensate for that loss. This put Serbian and Bulgarian territorial claims directly against each other.

Bulgaria Attacks, June 29th, 1913On the 29th of June, 1913, Bulgarian forces attacked Serbian and Greek positions in Macedonia without a formal declaration of war. Bulgaria's leaders calculated that a quick strike would force a renegotiation on better terms. Instead, the surprise attack brought Serbia, Greece, Romania, and the Ottoman Empire into the fight against Bulgaria.

The Second Balkan War BeginsRomania entered the war against Bulgaria from the north, and Ottoman forces moved to retake Thrace from the south. Bulgaria was quickly surrounded and unable to hold its gains. The resulting Treaty of Bucharest, signed on the 10th of August, 1913, stripped Bulgaria of most of what it had won in the first war and left deep resentment that fed into the overall tensions leading toward World War I.

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Major Events of the Second Balkan War

Ferdinand I of Bulgaria was upset following the First Balkan War, because he believed that Bulgaria had not gained the territories that it was owed.  As such, Bulgaria was the country that began the Second Balkan War.​

The Second Balkan War officially began on June 29th, 1913 following a period in which Bulgaria readied its armies.  The main opponents that the Bulgarians faced in the conflict were Serbia and Greece, which were both former allies to Bulgaria in the First Balkan War.  Both Serbia and Greece had signed a secret alliance before the outbreak of the Second Balkan War and were the main nations that Bulgaria argued with over territories in the Balkans.

The Bulgarian armies attacked Serbian forces on June 29th.  The two nations fought in bloody battles that included the Battle of Bregalnica, where the Bulgarians suffered heavy losses and were forced to retreat, and the Battle of Kalimanci, where Bulgaria stopped a Serbian advance.  Bulgaria did much better against the Greek forces but did not obtain any meaningful victory.  For instance, in the Battle of Kresna Gorge, which took place in July of 1913, both sides suffered losses.

As a result, the battle was a stalemateA situation in a battle where neither side can defeat the other and the fighting produces no clear winner. and neither Greece nor Bulgaria was able to defeat the other.  At the same time, both Romania and the Ottoman Empire attacked Bulgaria.  Romania had lingering tensions from the First Balkan War with Bulgaria and wanted to capture some more territories for themselves.  As well, the Ottoman Empire used the Second Balkan War as an opportunity to recapture territories that they had just lost in the First Balkan War.  The roles of both Romania and the Ottoman Empire were brief and did not carry the same intensity as the fighting carried out by both Serbia and Greece.

Regardless, Bulgaria suffered heavy losses in the Second Balkan War and sought a way out when the opposing forces threatened to capture the capital city Sofia.  The Second Balkan War ended on August 10th, 1913.​

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attacked from every side!★ Battle of Bregalnicalost in about six weeksknow the order!

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Second Balkan War, 1913

June 29th, 1913: Bulgaria attacks Serbian and Greek positions in Macedonia.

July 1913: Serbia defeats Bulgaria at the Battle of Bregalnica, forcing a retreat.

July 1913: Romania invades Bulgaria from the north, and Ottoman troops retake Adrianople.

July 1913: Greek and Bulgarian armies fight to a standstill at Kresna Gorge.

August 10th, 1913: The Treaty of Bucharest ends the war and takes land from Bulgaria.

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Outcomes of the Second Balkan War

As stated above, the Second Balkan War did not last long.  In fact, the total duration of the war was just over a month.  It ended in August of 1913 when Bulgaria sought an end to the war, after suffering terrible losses.  What resulted were two treaties: the Treaty of BucharestThe August 10th, 1913 agreement that forced Bulgaria to give up territories to Romania, Serbia, Montenegro, and Greece. and the Treaty of Constantinople.  The Treaty of Bucharest was completed first and involved Bulgaria and its main Balkan opponents in the war, which included: Romania, Serbia, Montenegro and Greece.

The Treaty of Bucharest was signed on August 10th, 1913 and modified the terms of the Treaty of London, which ended the First Balkan War.  In general, Bulgaria was forced to give up territories to each of the Balkan nations.  The Treaty of Constantinople was signed on September 29th, 1913 and was in regard to Bulgaria and the Ottoman Empire.  It was similar to the Treaty of Bucharest, in that it forced Bulgaria to provide territories to the Ottoman Empire.​

Besides the treaties mentioned above, historians consider the Second Balkan War to be significant for the role it played in the build up to World War I. In fact, both the First Balkan War and the Second Balkan War are considered to be significant causes of World War I, which began in 1914.​

The event that sparked World War I was the assassination of the Austrian Archduke Franz Ferdinand on June 28th, 1914.  Austria blamed Serbia for this action, since Ferdinand was murdered by Gavrilo Princip – a Bosnian Serb nationalist who had been armed and trained by the Black HandA secret organization dedicated to promoting Serbian and Slavic nationalism that armed and trained the men who assassinated Archduke Franz Ferdinand..  The Black Hand was a secret organization aimed at promoting Serbian (and Slavic) nationalism, and helped plan the assassination of Ferdinand in protest of Austria’s influence in the Balkans.  As such, this displays that World War I was a direct result of the Bosnian Crisis of 1908 and the two Balkan Wars.

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Two treaties ended the Second Balkan War of 1913, but they settled different conflicts and left different borders.

	Treaty of Bucharest (1913)	Treaty of Constantinople (1913)
Signed	August 10th, 1913	September 29th, 1913
Parties	Bulgaria, Serbia, Greece, Romania, Montenegro	Bulgaria and the Ottoman Empire
Conflict settled	Second Balkan War among Balkan states	Bulgarian-Ottoman fighting in the Second Balkan War
Main territorial change	Bulgaria lost much of the land it had won in the First Balkan War	Bulgaria returned Edirne and eastern Thrace to the Ottomans
Key outcome	Redrawn Balkan borders increased tensions among great powers	Ottoman Empire recovered significant European territory it had lost in 1912 and 1913
Role in WWI path	Left Bulgaria bitter toward Serbia, and Bulgaria joined the Central Powers in 1915	Showed the Ottoman Empire could still win back land in Europe

Treaty of Bucharest (1913)

Signed

August 10th, 1913

Parties

Bulgaria, Serbia, Greece, Romania, Montenegro

Conflict settled

Second Balkan War among Balkan states

Main territorial change

Bulgaria lost much of the land it had won in the First Balkan War

Key outcome

Redrawn Balkan borders increased tensions among great powers

Role in WWI path

Left Bulgaria bitter toward Serbia, and Bulgaria joined the Central Powers in 1915

Treaty of Constantinople (1913)

Signed

September 29th, 1913

Parties

Bulgaria and the Ottoman Empire

Conflict settled

Bulgarian-Ottoman fighting in the Second Balkan War

Main territorial change

Bulgaria returned Edirne and eastern Thrace to the Ottomans

Key outcome

Ottoman Empire recovered significant European territory it had lost in 1912 and 1913

Role in WWI path

Showed the Ottoman Empire could still win back land in Europe

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Cite This Article

To cite this article as a source, use one of the formats below.

MLA: Beck, Elias. “Second Balkan War: A Detailed Summary.” HistoryCrunch, 29 September 2026, https://historycrunch.com/second-balkan-war/.

APA: Beck, E. (2026). Second Balkan War: A Detailed Summary. HistoryCrunch. https://historycrunch.com/second-balkan-war/

Chicago: Beck, Elias. “Second Balkan War: A Detailed Summary.” HistoryCrunch. September 29, 2026. https://historycrunch.com/second-balkan-war/

Sources

• Hew Strachan, The First World War.
• Imperial War Museum
• Fordham Modern History Sourcebook