Dirigible in Brest-Litovsk Fortress

On August 4th, 2015, Warsaw, the capital of Russian Poland, surrendered to Germans without a fight. Fortresses at Kovno and Brest-Litovsk, among several others, capitulated. By September 18th when the fortress at Vilna surrenders to German forces the rout was complete. The German and Austro-Hungarian forces had pushed the Eastern Front 500 kilometers (310 miles) back. This unprecedented outcome became known as the Great Retreat to the Russians.