Treaty of Constantinople

The Treaty of Constantinople, signed on 16 September 1913, officially ended the military conflict between the Kingdom of Bulgaria and the Ottoman Empire that had arisen during the Second Balkan War. At that time, Bulgaria was ruled by Tsar Ferdinand I of Saxe-Coburg and Gotha, and the Ottoman Empire by Sultan Mehmed V. The document settled territorial matters left unresolved by the earlier Treaty of Bucharest (10 August 1913), to which the Ottoman Empire was not a party.
The treaty established the Bulgarian–Turkish border, leaving most of Eastern Thrace within the Ottoman Empire, except for the districts of Mustafa Pasha (present-day Svilengrad), Malko Tarnovo and Vasiliko (present-day Tsarevo). It also allowed the Kingdom of Bulgaria to reoccupy Western Thrace, including the Aegean coast between the mouths of the Maritsa and Mesta rivers.
The population of the territories ceded to Bulgaria had four years to choose whether to remain Bulgarian subjects or take Ottoman nationality. Those who chose to renounce Bulgarian nationality were required to leave Bulgaria but were guaranteed the right to retain their personal property. Muslims in these lands were exempted from military service. The Kingdom of Bulgaria assumed control over the railways in the newly acquired Bulgarian lands.