A Bulgarian postal cover from World War I, postmarked at Bucharest on 18 March 1918. This is from the end of the Romanian campaign in which the Central Powers defeated Romania. Romania entered into an armistice with the Central Powers on 17 December 1917 and opened peace negotiations.
Romania was forced to sign the Treaty of Bucharest on 7 May 1918, surrendering to the Central Powers. The treaty awarded Bulgaria the return of the southern Dobruja, control of the southern part of the northern Dobruja, and joint administration of the rest along with the other Central Powers.
This arrangement was short lived, however, as the Macedonian front collapsed a few months later and the Bulgarians sued for peace. The allied forces signed the Armistice with Bulgaria on 29 September 1918, effectively ending Bulgaria’s participation in the war.