First Battle of the Masurian Lakes
The loss of 125,000 soldiers did little damage to the  800,00 -man Russian Army. But it also meant a loss of about 150 artillery cannons. At the time these were very valuable for the old Russian army. The Germans also had heavy casualties. This showed the German advantage of their modern rail system for supplying and arming their soldiers. But, the push made by the Germans into Russia caused their defeat at the Battle of Augustov. The victories at Tannenberg and Masurian Lakes made Hindenburg a hero in Germany. As a result of his fame, in 1916 he became Chief of the German Staff.