Invasion of Romania September 1916–January 1917

Romania’s rationale for entering the war was, as with Italy, irredentist, to reclaim territories with Romanian-speaking populations from the Austro-Hungarian Empire. However, their invasion of Transylvania in pursuit of this end would reap the whirlwind. The invasion began on 19 August 1916, banking on the Central Powers’ distraction by both the Somme and Brusilov Offensives. This was a disastrous miscalculation: within weeks, two Austro-German armies had counterattacked, led by Falkenhayn and Mackensen, two of Germany’s premier generals. Mackensen, attacking from the south, first captured the fortress of Tutracaia then swept northeast to take the Black Sea port of Constanta. Meanwhile, Falkenhayn set the Transylvanian invasion force to flight, leaving Mackensen free to take the capital, Bucharest, on 6 December. The British fired the Ploesti oilfields to prevent them falling into German hands, while Romania’s remaining armed forces and government fled to Jassy by the Russian border.