It was formed just prior to the outbreak of hostilities from the units of Warsaw Military District and was mobilized in August 1914.

The result was that the Russians were now broadcasting their orders on unsecure lines, which were being intercepted and translated by German operators.

While sluggish due to supply shortages, poor logistics, and misuse of railway lines, the 2nd Army's advance was relatively unopposed until 22 August when it encountered German forces all along its front.

Unbeknown to Samsonov, the German command, who had been receiving intercepted Russian orders involving troop movements, had already shifted forces to the south to check his advance and when further orders were intercepted with news that he had changed his direction, German forces were able to adjust their positions and threaten the now exposed left and right flanks of the 2nd Army.

Unaware that his right flank was now exposed, Samsonov pressed the 2nd Army on and repeatedly engaged the XX Corps.

With the centre also facing critical supply shortages the assault was halted before an order to retreat to the southeast was given.

However, not all of its units were destroyed, and the army remained in the line, participating in the First Battle of the Masurian Lakes in early September, 1914.

It continued to participate in the fighting on the Eastern Front until the dissolution of the Imperial Russian Army in early 1918.