First Battle of the Masurian Lakes The First Battle of the Masurian Lakes was a German offensive in the Eastern Front during the early stages of World War I . It pushed the Russian First Army back across its entire front , eventually ejecting it from Germany in disarray . Further progress was hampered by the arrival of the Russian Tenth Army on the Germans ' left flank . Although not as devastating as the Battle of Tannenberg that took place a week earlier , the battle nevertheless upset Russian plans into the spring of 1915 . Background . The Russian offensive in the east had started well enough , with General Rennenkampf ' s 1st Army ( Army of the Neman ) forcing the Germans westward from the border towards Königsberg . Meanwhile the Russian Second Army approached from the south , hoping to cut the Germans off in the area around the city . However , Colonel Max Hoffmann developed a plan to attack the Second Army as it attempted to maneuver north over some particularly hilly terrain . Hoffman ' s plan was quickly implemented , culminating in the complete destruction of the Second Army at the Battle of Tannenberg between 26 and 30 August 1914 . The counter - offensive was made possible , in part , due to the personal enmity between the two Russian Generals — which was well known to the Germans . The commander of the Second , Alexander Samsonov , had publicly criticized Rennenkampf some years earlier ( about the Battle of Mukden in 1905 ) , and it is said that the two had come to blows over the matter . When Samsonov became aware of the German movements he requested that the gap between the two armies be closed up , but Rennenkampf was in no hurry to act on this , leaving Samsonov isolated many miles to the southwest . When the nature of the German counteroffensive became clear , Rennenkampf had his troops move as quickly as possible to help , but by then it was too late . By the time the battle proper ended on 30 August ( Samsonov committed suicide on 29 August ) , the closest of Rennenkampf ' s units , his II Corps , was still over 45 miles ( 70 km ) from the pocket . In order to get even this close his units had to rush southward , and were now spread out over a long line running southward from just east of Königsberg . An attack by the German Eighth Army from the west would flank the entire army . Of course the Germans were also very far away , but unlike the Russians , the Germans could easily close the distance using their extensive rail network in the area . On 31 August , with Tannenberg lost , Rennenkampf had been ordered to stand his ground in the event of a German attack . Realizing his forces were too spread out to be effective , he ordered a withdrawal to a line running from Königsberg ' s defensive works in the north , to the Masurian Lakes near Angerburg in the south , anchored on the Omer River . Bolstering his forces were the newly formed XXVI Corp , which he placed in front of Königsberg , moving his more experienced troops south into the main lines . His forces also included two infantry divisions held in reserve . All in all , he appeared to be in an excellent position to await the arrival of the Russian Tenth Army , forming up to his south . Battle . German efforts at mopping up the remains of the Second Army were essentially complete by 2 September and Paul von Hindenburg immediately started moving his units to meet the southern end of Rennenkampf ' s line . He was able to safely ignore the Russian right ( in the north ) , which was in front of the extensive defensive works outside of Königsberg . Adding to his force were two newly arrived Corps from the Western Front , the Guards Reserve Corps and the XI Corps . For the first time since the opening of the war , the Germans now had numerical superiority . Then , like Rennenkampf , Hindenburg fed his newest troops into the northern end of the line and planned an offensive against the south . But unlike Rennenkampf , Hindenburg had enough forces not only to cover the entire front in the Insterburg Gap , but had additional forces " left over " . He sent his most capable units , the I Corps and XVII Corps , far to the south of the lines near the middle of the Lakes , and sent the 3rd Reserve Division even further south to Lyck , about 30 miles from the southern end of Rennenkampf ' s line . Hindenburg ' s southern divisions began their attack on the 7th of September , with the battle proper opening the next day . Throughout the 8th of September the German forces in the north hammered at the Russian forces facing them , forcing an orderly retreat eastward . In the south , however , things were going much worse . The German XVII Corps had met their counterpart , the Russian II , but were at this point outnumbered . The II maneuvered well , and by the end of the day had managed to get their left flank into position for a flanking attack on the Germans , potentially encircling them . However , all hope of a victory vanished the following day when then the German I Corps arrived in support of the XVII ; now the Russians were outflanked . Meanwhile the 3rd Reserve Divisions had engaged the Russians ' XXII Corps even further south , and after a fierce battle forced them to fall back southeastward ; its commander wired Rennenkampf he had been attacked and defeated near Lych , and could do nothing but withdraw . Rennenkampf ordered a counteroffensive in the north to buy time to reform his lines , managing to push the German XX Corps back a number of miles . However the Germans did not stop to reform their lines but instead continued their advances in the south and north . This left the victorious Russian troops isolated , but they were able to retreat to new lines being set up in the east . Now the battle turned decisively in the Germans ' favor . By 11 September the Russians had been pushed back to a line running from Insterburg to Angerburg in the north , with a huge flanking maneuver developing to the south . It was at this point that the threat of encirclement appeared possible . Rennenkampf ordered a general retreat toward the Russian border , which happened rapidly under the protection of a strong rear guard . It was this speed that enabled the retreating Russian troops to escape the trap Hindenburg had planned for them . The German commander had ordered his wings to quicken their march as much as possible , but a trivial accident — a rumor of a Russian counterattack — cost the Germans half a day ' s march , allowing the Russians to escape to the east . These reached Gumbinnen the next day , and Stallupönen on the 13th . The remains of the First Army retreated to the safety of their own border forts . Likewise , the Tenth Army was forced back into Russia . Outcome . The Eighth Army had now completed one of the most astounding victories in history , completely destroying the Second Army , mauling the First , and ejecting all Russian troops from German soil . Meanwhile , new German corps ( under von der Goltz ) were able to use this movement to safely move into position to harass the scattered remains of the Second Army , while far to the southwest the new German Ninth was forming up . It would not be long before they were able to face the Russians in a position of numerical superiority . However , this advantage was bought at a cost : the newly arrived corps had been sent from the Western front and their absence would be felt in the upcoming Battle of the Marne . In addition , although these German victories were strategically significant , the main battles of the Eastern Front were to take place between Austria - Hungary and Russia far to the south , where the Russian forces were initially able to rout the Austro - Hungarian army . It took another year before the German and Austro - Hungarian forces were finally able to reverse the Russian advances , pushing them out of Galicia and then Russian Poland .