In the First Balkan War, the coalition of Bulgaria, Serbia, Greece and Montenegro defeated the Ottoman Empire.

The Ottomans lost nearly all their European possessions, save for a small territory around the Sea of Marmara by the Treaty of London.

[3] Although peace talks between Bulgaria and her other neighbours were held in Bucharest, the Ottoman Empire was not represented there and conducted separate negotiations which led to the Treaty of Constantinople.

The Ottoman Empire and Bulgaria were allies in the Central Powers in the First World War.

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