Romania joined the war on 27 August 1916, launching an invasion of Transylvania. When this failed due to a German-led Central Powers counterattack, the Romanians subsequently succeeded in defeating the attempts made by the Central Powers to pressure every mountain pass and exploit a success wherever it was achieved. Changing his strategy, German General Erich von Falkenhayn selected a single mountain pass — along the Jiu Valley — for a breakthrough. He chose that particular place on logistical grounds, as the valleys elsewhere were too narrow for the Germans to make best use of their superiority in firepower.