The Battle of Transylvania was the first major operation of Romania during World War I, beginning on 27 August 1916. It started as an attempt by the Romanian Army to seize Transylvania, and potentially knock Austria-Hungary out of the war. Although initially successful, the offensive was brought to a halt after Bulgaria's attack on Dobruja. Coupled with a successful German and Austro-Hungarian counterattack which started in mid-September, the Romanian Army was eventually forced to retreat back to the Carpathians by mid-October. The Romanian armies however managed to escape the Central Powers' attempts to completely destroy them. The Battle of Transylvania also caused the replacement of the Chief of Staff of the German Army and the shifting of German attention to the region, causing German offensive operations at Verdun to cease.

The Kingdom of Romania was a constitutional monarchy that existed from 13 March (O.S.) / 25 March 1881 with the crowning of prince Karl of Hohenzollern-Sigmaringen as King Carol I, until 1947 with the abdication of King Michael I and the Romanian parliament's proclamation of the Romanian People's Republic.