On the Greek side, Lambros Koromilas had proposed the international control of the area
of the Straits and Constantinople, the grant of western Thrace (between the Rivers Nestos and Evros) to Bulgaria, and the area of Macedonia between Kavala,
Thessaloniki and as far as Avlona on the shores of the Adriatic Sea, to Greece.
Bulgaria demanded the implementation of the terms of the Treaty of San Stephano,
it claimed, that is, the whole of Macedonia as far as Monastir. It was evident
that under these conditions no understanding would be feasible.
At the same time, Bulgaria had strong disputes with Serbia concerning the distribution
of northern Macedonia that had been captured by the Serbian army.
These facts led to the formation of a common Greco-Serbian front against Bulgaria, ratified
with friendship and a mutual protection treaty between Greece and Serbia, signed in Thessaloniki on 19 May/1 June 1913. According to this treaty, the borders of the two countries were defined (similar to the present ones) recognizing essentially the fait accompli caused by the occupation of
territories by the two armies, but commercial facilities were provided to the Serbs in the port of
Thessaloniki. Next, the claims of the two countries on Bulgaria were outlined, to be resolved
through international arbitration. In the event of the latter's refusal to consent to such a
perspective, a clash would be inevitable.
The Treaty only exacerbated the crisis. On 17/30 June 1913 Bulgarian forces
attacked the Greek and Serbian positions in Macedonia. On that same day the Greek side demanded
the evacuation of Thessaloniki by the Bulgarian garrison that had been stationed there since October.
The refusal led to clashes within the city, leaving several
dead and ending in the capture of the whole Bulgarian military force. There followed the Battles
of Kilkis-Lachanas and Doirani, in which Greek troops were victorious, a fact
that allowed the capture of Kilkis, Drama and Serres by the Greek army, while forces of the
Greek Navy captured Kavala and were forwarded to western Thrace. On 18 July an armistice
was signed that found the Bulgarian troops at a disadvantage. The final arrangements
came about with the Treaty of Bucharest.