Though the Balkan allies had fought together against the common enemy, that was not enough to overcome their mutual rivalries.
In the original document for the Balkans league, Serbia promised Bulgaria most of Macedonia.
But before the first war come to an end, Serbia (in violation of the previous agreement) and Greece revealed their plan to keep possession of the territories that their forces had occupied.
This act prompted the tsar of Bulgaria to invade his allies.
The Second Balkan War broke out on 29 (16) June 1913, when Bulgaria attacked its erstwhile allies in the First Balkan War, Serbia and Greece, while Montenegro and the Ottoman Empire intervened later against Bulgaria, with Romania attacking Bulgaria from the north in violation of a peace treaty.

When the Greek army had entered Thessaloniki in the First Balkan War ahead of the Bulgarian 7th division by only a day, they were asked to allow a Bulgarian battalion to enter the city.
Greece accepted in exchange for allowing a Greek unit to enter the city of Serres.
The Bulgarian unit that entered Thessaloniki turned out to be an 18,000-strong division instead of the battalion, which caused concern among the Greeks, who viewed it as a Bulgarian attempt to establish a condominium over the city.
In the event, due to the urgently needed reinforcements in the Thracian front, Bulgarian Headquarters was soon forced to remove its troops from the city (while the Greeks agreed by mutual treaty to remove their units based in Serres) and transport them to Dedeağaç (modern Alexandroupolis), but still it left behind a battalion that started fortifying its positions.

Greece had also allowed the Bulgarians to control the stretch of the Thessaloniki-Constantinople railroad that lay in Greek-occupied territory, since Bulgaria controlled the largest part of this railroad towards Thrace.
After the end of the operations in Thrace, and confirming Greek concerns, Bulgaria was not satisfied with the territory it controlled in Macedonia and immediately asked Greece to relinquish its control over Thessaloniki and the land north of Pieria, effectively handing over all Aegean Macedonia.
These unacceptable demands, with the Bulgarian refusal to demobilize its army after the Treaty of London had ended the common war against the Ottomans, alarmed Greece, which decided to also keep its army mobilized.
A month after the Second Balkan War started, the Bulgarian community of Thessaloniki no longer existed, as hundreds of long-time Bulgarian locals were arrested.
Thirteen hundred Bulgarian soldiers and about five hundred komitadjis were also arrested and transferred to Greek prisons.
In November 1913, the Bulgarians were forced to admit their defeat, as the Greeks received international recognition on their claim of Thessaloniki .

Similarly, in North Macedonia, the tension between Serbia and Bulgaria due to the latter's aspirations over Vardar Macedonia generated many incidents between their respective armies, prompting Serbia to keep its army mobilized.
Serbia and Greece proposed that each of the three countries reduce its army by one fourth, as a first step to facilitate a peaceful solution, but Bulgaria rejected it.
Seeing the omens, Greece and Serbia started a series of negotiations and signed a treaty on 1 June(19 May) 1913.
With this treaty, a mutual border was agreed between the two countries, together with an agreement for mutual military and diplomatic support in case of a Bulgarian or/and Austro-Hungarian attack.
Tsar Nicholas II of Russia, being well informed, tried to stop the upcoming conflict on 8 June, by sending an identical personal message to the Kings of Bulgaria and Serbia, offering to act as arbitrator according to the provisions of the 1912 Serbo-Bulgarian treaty.
But Bulgaria, by making the acceptance of Russian arbitration conditional, in effect denied any discussion, causing Russia to repudiate its alliance with Bulgaria (see Russo-Bulgarian military convention signed 31 May 1902).

The Serbs and the Greeks had a military advantage on the eve of the war because their armies con
Though the Balkan allies had fought together against the common enemy, that was not enough to overcome their mutual rivalries. In the original document for the Balkans league, Serbia promised Bulgaria most of Macedonia. But before the first war come to an end, Serbia (in violation of the previous agreement) and Greece revealed their plan to keep possession of the territories that their forces had occupied. This act prompted the tsar of Bulgaria to invade his allies. The Second Balkan War broke out on 29 (16) June 1913, when Bulgaria attacked its erstwhile allies in the First Balkan War, Serbia and Greece, while Montenegro and the Ottoman Empire intervened later against Bulgaria, with Romania attacking Bulgaria from the north in violation of a peace treaty.
When the Greek army had entered Thessaloniki in the First Balkan War ahead of the Bulgarian 7th division by only a day, they were asked to allow a Bulgarian battalion to enter the city. Greece accepted in exchange for allowing a Greek unit to enter the city of Serres. The Bulgarian unit that entered Thessaloniki turned out to be an 18,000-strong division instead of the battalion, which caused concern among the Greeks, who viewed it as a Bulgarian attempt to establish a condominium over the city. In the event, due to the urgently needed reinforcements in the Thracian front, Bulgarian Headquarters was soon forced to remove its troops from the city (while the Greeks agreed by mutual treaty to remove their units based in Serres) and transport them to Dedeağaç (modern Alexandroupolis), but still it left behind a battalion that started fortifying its positions.
Greece had also allowed the Bulgarians to control the stretch of the Thessaloniki-Constantinople railroad that lay in Greek-occupied territory, since Bulgaria controlled the largest part of this railroad towards Thrace. After the end of the operations in Thrace, and confirming Greek concerns, Bulgaria was not satisfied with the territory it controlled in Macedonia and immediately asked Greece to relinquish its control over Thessaloniki and the land north of Pieria, effectively handing over all Aegean Macedonia. These unacceptable demands, with the Bulgarian refusal to demobilize its army after the Treaty of London had ended the common war against the Ottomans, alarmed Greece, which decided to also keep its army mobilized. A month after the Second Balkan War started, the Bulgarian community of Thessaloniki no longer existed, as hundreds of long-time Bulgarian locals were arrested. Thirteen hundred Bulgarian soldiers and about five hundred komitadjis were also arrested and transferred to Greek prisons. In November 1913, the Bulgarians were forced to admit their defeat, as the Greeks received international recognition on their claim of Thessaloniki .
Similarly, in North Macedonia, the tension between Serbia and Bulgaria due to the latter's aspirations over Vardar Macedonia generated many incidents between their respective armies, prompting Serbia to keep its army mobilized. Serbia and Greece proposed that each of the three countries reduce its army by one fourth, as a first step to facilitate a peaceful solution, but Bulgaria rejected it. Seeing the omens, Greece and Serbia started a series of negotiations and signed a treaty on 1 June(19 May) 1913. With this treaty, a mutual border was agreed between the two countries, together with an agreement for mutual military and diplomatic support in case of a Bulgarian or/and Austro-Hungarian attack. Tsar Nicholas II of Russia, being well informed, tried to stop the upcoming conflict on 8 June, by sending an identical personal message to the Kings of Bulgaria and Serbia, offering to act as arbitrator according to the provisions of the 1912 Serbo-Bulgarian treaty. But Bulgaria, by making the acceptance of Russian arbitration conditional, in effect denied any discussion, causing Russia to repudiate its alliance with Bulgaria (see Russo-Bulgarian military convention signed 31 May 1902).
The Serbs and the Greeks had a military advantage on the eve of the war because their armies con
Balkan Wars