The Germans, led by Supreme Commander of All German Forces in the East Paul von Hindenburg, would attack eastward from their front line in western Poland, which had been occupied after the Battle of Łódź in 1914, toward the Vistula River and also in East Prussia in the vicinity of the Masurian Lakes (site of the 1914 Battle of the Masurian Lakes).

According to Prit Buttar, "It was with considerable reluctance that Falkenhayn agreed to the deployment of four additional corps on the Eastern Front in early 1915.

Whilst he remained convinced of the primacy of the Western Front, the failure to win a decisive victory there left him unable to counter the arguments of Hindenburg and Ludendorff...might be able to inflict a sufficiently heavy defeat upon Russia to end the conflict in the east."

Ludendorff wrote, "It was agreed with OHL to use the four corps to strike against the enemy forces deployed against Eighth Army as soon as they arrived.

[12] Chief of the German Great General Staff Erich von Falkenhayn strongly believed that the war would be won on the Western Front.

[15] In East Prussia, further Russian incursions were blocked by trench lines extending between the Masurian Lakes; they were held by the German Eighth Army, commanded by General Otto von Below.

A new Russian Twelfth Army under General Pavel Plehve was assembling in Poland roughly 100 km (62 mi) to the southwest.

On February 7, despite a heavy snowstorm, the left wing of Below's Eighth Army launched a surprise attack against Sievers, whose trenches were shallow, disconnected ditches, with little or no barbed wire because the first shipments had not arrived until December 1914.

Despite these formidable obstacles, the German pincers advanced 120 km (75 mi) in a week, inflicting severe casualties on the Russians.

Nikolai Epanchin's III Corps, which had already lost most of its equipment, withdrew to Kovno and Olita, where they no longer became a factor in the battle.

On 14 February, the German Tenth Army's XXI Corps, under the command of Fritz von Below, cut the road connecting Augustowo to Sejny.

Before the retreat to Frącki (no more than 250 men remained), the artillerymen managed to remove locks and sights from 8 guns and drown them in a swamp.

At the Gaienek Village, the Russian regiments, which continued to advance forward, dispersed one battalion and captured 2 more guns, but were stopped.

On February 18, the Germans who surrounded the XX Corps began to eliminate it, the defense of the outer front of the encirclement was assigned to the R. Kosh group, reinforced by the Königsberg Landwehr, the 1st Cavalry Division and the 5th Guards Brigade.

K. Litzman's group and the 4th Cavalry Division were transferred to the 10th Army to develop the offensive against the Bobr River and assist in the encirclement of Osowiec.

At Augustow, the corps suffered heavy losses, artillery parks, carts, divisional infirmaries, two light and mortar batteries were abandoned, but the infantry broke out of the already closing ring.

But for the group of General Bulgakov, the path to salvation was closed, and the retreating neighboring corps were never sent by Thadeus von Sivers on a counteroffensive to break through the ring from the outside.

[25] The "Winter Battle in Masuria" ended with the expulsion of the Russian troops of the 10th Army from the borders of East Prussia, inflicting heavy losses on them and capturing parts of four infantry divisions.

But more active actions on the Russian side could not only prevent the XX Army Corps from dying, but also turn the tide of battles.

Much of Sievers' Tenth Army escaped the German attempts to create an encirclement to rival Tannenberg, albeit with substantial losses."

Yuri Danilov, the Russian quartermaster general, stated, "This offensive by the German Eighth and Tenth Armies in February 1915 was definitely a great success for our enemies.

Our plan to secure this province in order to anchor our right flank and to advance on the lower Vistula was rendered impossible by the German tactical victory.