stylistic:tone, structural:summarization, information:highlighting, stylistic:style_transfer
German theatre

By August 1914, Russia had invaded with unexpected speed the German province of East Prussia, ending with a humiliating defeat at Tannenberg, owing to a message sent without wiring and coding, causing the destruction of the entire second army. Russia suffered a massive defeat at the Masurian Lakes twice, the first ending with a hundred thousand casualties; and the second suffering 200,000. By October, the German Ninth Army was near Warsaw, and the newly-formed Tenth Army had retreated from the frontier in East Prussia. Grand Duke Nicholas, the Russian commander-in-chief, now had the order to invade Silesia with his Fifth, Fourth, and Ninth armies. The Ninth Army, led by Mackensen, retreated from the frontline in Galicia and concentrated between the cities of Posen and Thorn. The advance took place on 11 November against the main army's right flank and rear; the First and Second armies were severely mauled, and the Second army was nearly surrounded in Łódź on 17 November.

Exhausted Russian troops began to withdraw from Russian-held Poland, allowing the Germans to capture many cities, including the kingdom's capital Warsaw on 5 August 1915. In the same month, the emperor dismissed Grand Duke Nicholas and took personal command, this was a turning point for the Russian army and the beginning of the worst disaster. The Germans continued pushing the front until they were halted in the line from Riga to Tarnopol. Russia lost the entire territory of Poland and Lithuania, part of the Baltic states and Grodno, and partly of Volhynia and Podolia in Ukraine; thereafter the front with Germany was stable until 1917.