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.