Treaty of Constantinople, signed on 29 September 1913 between the Ottoman Empire and the Kingdom of Bulgaria after the Second Balkan War.

Treaty of Constantinople has signed on 29 September 1913 between the Ottoman Empire and the Kingdom of Bulgaria after the Second Balkan War at the Ottoman capital Constantinople(modern-day İstanbul).


In the First Balkan War, the Ottoman Empire was defeated by the alliance of Bulgaria, Serbia, Greece, and Montenegro. The Ottomans lost almost all their European territories, save for a small territory around the Sea of Marmara by the Treaty of London.

The Ottomans still were capable to recover Eastern Thrace during the Second Balkan War. Although peace talks between Bulgaria and her other neighbors were held in Bucharest, the Ottoman Empire was not represented there and conducted separate negotiations which led to the Treaty of Constantinople.

Terms of Treaty of Constantinople

The terms of the treaty Treaty of Constantinople were:

  1. Bulgaria recognized Ottoman gains of Edirne, Kırklareli, and Didymoteicho and the surrounding territory.
  2. The Ottoman Empire ceded the port of Dedeagach (mod. Alexandroupoli) to Bulgaria.
  3. The transfer of lands was to be completed within 10 days.
  4. The armies on the border would be withdrawn within three weeks.
  5. Prisoners of war from both sides would be released.
  6. Both political and economic ties between the two countries would be restored.

The treaty mostly represents the modern-day boundaries between Eastern Thrace (European Turkey), Bulgaria, and Greece.


The Ottoman Empire and Bulgaria were allies in the Central Powers in the First World War. Before the Bulgarian entry into the war, the Ottoman government chose to cede Didymoteicho to Bulgaria (probably to persuade Bulgaria to join the war) by way of the Bulgarian–Ottoman convention (1915). 

However, the Central Powers were defeated in 1918 and Bulgaria lost both Western Thrace and Didymoteicho to Greece.

Under the terms of the failing Treaty of Sèvres, Turkey was to cede almost all of Eastern Thrace to Greece, but the stated territorial changes were negated by Turkey’s victory over Greece in the War of Independence and the subsequent Treaty of Lausanne, which reaffirmed the borders set by the Constantinople agreement and the Bulgarian-Ottoman convention. (except Didymoteicho)

>>>Treaty of Constantinople, 1832

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