On this date in 1916, the Kingdom of Romania declared war on Germany and Austria. Its troops had already been mobilized. They crossed the border and began a headlong advance into Transylvania.
Kaiser Wilhelm panicked: “The war is lost!”
Then the Central Powers counterattacked — any Allied hope failed that the Germans might have been otherwise engaged in the Battle of the Somme while the Austro-Hungarians had their hands full with the Russians with the Brusilov Offensive.
Despite many setbacks, including the fall of Bucharest to the Germans in December, the Romanians fought on. In the spring of 1917, the Romanian Army had grown to 400,000 men, plus its air force.
But its great ally, Russia, became less and less effective as the country deteriorated. When the Revolution began. Romania was left isolated and surrounded. It signed an armistice with the Central Powers on Dec. 7, 1917.
Here’s news footage of the Romanian army versus the Austro-Hungarians.