In February 1915, the 3rd Siberian Army Corps participated in the Second Battle of the Masurian Lakes. On 7 February 1915, the German 8th Army attacked the left flank of the Russian 10th Army. The next day, the German 10th Army launched an offensive in the rear of the Russian 10th Army, inflicting a major blow on the right flank of the 3rd Siberian Army Corps, driving the 26th Army Corps out of its positions and forcing it to retreat. The retreat exposed the left flank of the 20th Army Corps, which the Germans subsequently surrounded and defeated in the vicinity of the Augustów Forest. On the left flank of the 10th Army in the Ełk–Rajgród sector. Radkevich's 3rd Siberian Corps alone confronted the German 8th and 10th Armies (totaling about three corps) and held off three German attacks, saving the 10th Army from complete destruction. Even the German General Erich Ludendorff