The First Battle of the Masurian Lakes was the second victory of the war by the Germans. General Paul von Hindenburg, commander of the German Eighth Army, turned his attention on the Russian First Army, commanded by Paul von Rennenkampf, and began his attack on September 7th. The Germans attacked from both sides of the southern lakes, aiming to push the Russians up the coast. The Russians were outnumbered 3 - to - 1 and dispersed their forces while the Germans continued northward in pursuit of the main body of the Russian army. Rennenkampf ordered withdraw on September 9th while also ordering a counter - attack at the Germans to hold them back while the rest of his army retreated. He succeeded in getting his army to safety but lost 125,000 men while the Germans lost, at most, 40,000 men. This battle largely removed any threat the Russians posed to the Germans stationed in East Prussia.