Before World War I, the 20th Corps was stationed in the Vilna Military District with its headquarters in Riga.

At the outbreak of the war, the corps consisted of two infantry divisions and a number of independent battalions and brigades.

During the Second Battle of the Masurian Lakes, the 20th Army Corps was led by General Pavel Illyich Bulgakov.

On February 7, in the middle of a snowstorm, Fritz von Below's German Eighth Army launched a surprise attack, advancing 70 miles (110 km) within one week.

They inflicted severe casualties on the Imperial Russian Army, resulting in its disorderly withdrawal with many of its soldiers being imprisoned.