The Second Balkan War (1913) was a conflict in which Bulgaria, unhappy with its share of territory from the First Balkan War, attacked its former allies Serbia and Greece, lost badly, and the Treaty of Bucharest left Serbia stronger, raising tensions with Austria-Hungary before World War I.
The Second Balkan War broke out in 1913, just weeks after the First Balkan War ended. In the first war, the Balkan League (Serbia, Bulgaria, Greece, and Montenegro) had teamed up to push the Ottoman Empire almost entirely out of Europe. Then they fought over the spoils. Bulgaria felt cheated out of Macedonia, so it attacked Serbia and Greece. That turned out to be a terrible bet. Romania and even the Ottomans piled on against Bulgaria, and the war ended quickly with the Treaty of Bucharest (1913), which stripped Bulgaria of most of its earlier gains.
For AP Euro, the war itself matters less than what it did to the balance of power. Serbia came out as the dominant Balkan state, which directly threatened Austria-Hungary, since Serbia's brand of Slavic nationalism appealed to millions of Slavs living inside the Austro-Hungarian Empire. The CED frames this under KC-3.4.III.E, which says nationalist tensions in the Balkans drew the Great Powers into a series of crises leading up to World War I. The Second Balkan War is the last of those crises before the assassination at Sarajevo in 1914.
This term lives in Unit 7, Topic 7.3 (National Unification and Diplomatic Tensions), under learning objective 7.3.B, which asks you to explain how nationalist sentiment and political alliances created tension among European powers from 1815 to 1914. The Second Balkan War is the final domino in the chain the CED lays out, running from the Congress of Berlin in 1878 through the growing influence of Serbia. It shows two big Unit 7 ideas colliding. Nationalism, which had built Italy and Germany, was now tearing the Ottoman-controlled Balkans apart. And the alliance system, which Bismarck had designed to keep the peace, had hardened into mutually antagonistic blocs after his dismissal in 1890. By the end of 1913, Serbia was emboldened, Bulgaria was bitter, Austria-Hungary was nervous, and Russia was committed to backing Serbia. One assassination later, the whole system detonated. If you can explain why this small regional war made a continental war more likely, you understand the heart of LO 7.3.B.
Keep studying AP® Euro Unit 7
Congress of Berlin (Unit 7)
The Congress of Berlin (1878) redrew the Balkan map to satisfy the Great Powers, not the Balkan peoples. The Second Balkan War is what happens 35 years later when those frustrated nationalist claims finally explode. The CED lists both as steps in the same chain of Balkan crises.
Bosnia-Herzegovina annexation crisis (Unit 7)
Austria-Hungary's 1908 annexation of Bosnia enraged Serbia, and the Second Balkan War then made Serbia stronger and bolder. Put the two together and you get the exact Austria-versus-Serbia hostility that turns the 1914 assassination into a world war.
Bismarck's dismissal (Unit 7)
After Bismarck was fired in 1890, his careful alliance system decayed into two rival blocs. That's why a Balkan squabble couldn't stay local. Russia backed Serbia, Germany backed Austria-Hungary, and every regional crisis carried Great Power stakes.
Crimean War (Unit 7)
The Crimean War first exposed the Ottoman Empire as the 'sick man of Europe' and broke the Concert of Europe (KC-3.4.II.A). The Balkan Wars of 1912-1913 are the endgame of that decline, as Balkan states carved up the Ottoman lands the Crimean War had shown were up for grabs.
Multiple-choice questions usually test this term through cause and effect. You might be asked which treaty ended the war (the Treaty of Bucharest), which Balkan League member turned on its allies (Bulgaria), which state emerged as the region's significant power (Serbia), or how the outcome affected Austria-Hungary's position (it felt increasingly threatened by a stronger Serbia). No released FRQ has used the term verbatim, but it fits perfectly into causation essays on the origins of World War I. The move the exam rewards is connecting the dots, not reciting battles. Use the Second Balkan War as specific evidence that Balkan nationalism plus the post-Bismarck alliance system made a general European war increasingly likely by 1914.
The First Balkan War (1912-1913) was the Balkan League versus the Ottoman Empire, and the League won, ejecting the Ottomans from almost all of Europe. The Second Balkan War (1913) was the League fighting itself, with Bulgaria attacking Serbia and Greece over the division of Macedonia. Easy way to keep them straight: first war, allies versus Ottomans; second war, allies versus each other.
The Second Balkan War (1913) started when Bulgaria, unhappy with its share of Ottoman territory from the First Balkan War, attacked its former allies Serbia and Greece.
Bulgaria lost quickly once Romania and the Ottoman Empire joined against it, and the Treaty of Bucharest (1913) stripped away most of Bulgaria's earlier gains.
Serbia emerged as the dominant Balkan power, which directly threatened Austria-Hungary because Serbian nationalism appealed to Slavs inside the Austro-Hungarian Empire.
The CED (KC-3.4.III.E) frames the war as one of a series of Balkan crises, alongside the Congress of Berlin and the Bosnia annexation crisis, that drew the Great Powers toward World War I.
The war shows the two big forces of Topic 7.3 working together: aggressive nationalism in the Balkans and a rigid alliance system that turned regional disputes into Great Power confrontations.
It was a 1913 conflict in which Bulgaria attacked its former Balkan League allies Serbia and Greece over the division of territory won from the Ottomans. Bulgaria lost, and the Treaty of Bucharest left Serbia as the strongest Balkan state.
Not directly, but it set the stage. It strengthened Serbia, deepened Austria-Hungary's fear of Slavic nationalism, and left Bulgaria resentful, so when Franz Ferdinand was assassinated in 1914, the region was already primed to explode. The CED treats it as one of the Balkan crises leading up to WWI.
The First Balkan War (1912-1913) was the Balkan League fighting the Ottoman Empire and winning. The Second Balkan War (1913) was the League turning on itself, with Bulgaria attacking Serbia and Greece over the spoils.
The Treaty of Bucharest (1913). It took most of Bulgaria's recent gains away and confirmed Serbia and Greece as the big winners in the Balkans.
Because Serbia came out of the war larger and more confident, and Serbian nationalism appealed to the millions of Slavs living inside Austria-Hungary. A strong Serbia looked like an existential threat to the multiethnic Habsburg empire, which is why Vienna reacted so aggressively in 1914.
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