After Romania entered World War I in August 1916 on the side of the Allies, the Third Army defended the border with Bulgaria, while the rest of the Romanian Army engaged in the Battle of Transylvania. When a Bulgarian-German army under August von Mackensen invaded Romania in September 1916, the Third Army made attempts to withstand the enemy offensive at Silistra, Bazargic, Amzacea and Topraisar, but had to withdraw under the pressure of superior enemy forces after the Second Battle of Cobadin. After the Flămânda Offensive, the Third Army was disbanded.