Battle of Bazargic

The Battle of Bazargic, also known as the Battle of Dobrich or the Dobrich epopee (), took place between 5 and 7 September 1916 between a joint Bulgarian–German–Ottoman force, consisting mainly of the Bulgarian Third Army, and a Romanian–Russian force, including a Division of Serbian Volunteers serving under the Russian 47th Corps. The battle was part of the Romanian campaign towards the end of 1916. It ended with a Central Powers victory.
Background.
Although bound by the pre-war Triple Alliance to the Central Powers, Romania instead joined the Triple Entente in August 1916, following the signing of the Treaty of Bucharest (1916). German Commander Field Marshal August von Mackensen was put in charge of the Romanian campaign in the Dobruja front. In September the 3rd Bulgarian Army was reinforced with two Ottoman divisions and part of a German division. The Central Powers' plan was to attack the Romanian forces in Transylvania, while at the same time attacking along the Black Sea, into the Dobruja, a region inhabited mainly by Bulgarians and assigned to Romania in 1913, as a result of the Second Balkan War and the ensuing Treaty of Bucharest (1913).
Battle.
Mackensen started with a surprise move on Turtucaia, a Romanian fortress. Although the besieging force was smaller than the garrison, most surrendered quickly to the Bulgarian 3rd Army after their commander fled. 
Along with German reinforcements, Bulgarian units on the Southern front who crossed the border and invaded the Dobruja found themselves facing the Romanian Third Army and two Russian infantry divisions. Some of the Romanian units had surrendered to the Russians, believing them to be Bulgarians. 
Simultaneously with the assault of the fortress of Turtucaia, the Bulgarian Third Army defeated the Romanian-Russian force, including the First Serbian Volunteer Division, at the Battle of Bazargic, despite their numerical superiority. The outnumbered forces of the Central Powers managed to push the Romanians and the Russians north, while the Serbian Volunteer division suffered heavy casualties with 8,539 dead and wounded. 
On 7 September after intense fighting the defeated Russian general ordered a withdrawal.
Aftermath.
As the Romanian army withdrew into Moldavia by the beginning of November, the Central Powers had captured the whole of Dobruja.