The Russian Empire entered World War I on 1 August 1914. On 7 August 1914, Radkevich returned to active duty and was re-appointed commander of the 3rd Siberian Army Corps, which became part of the new 10th Army. During the Russian invasion of East Prussia, the 10th Army began fighting the Imperial German Army's 8th Army in the Augustów Forest on 15 September 1914. Although the 10th Army's 2nd Caucasian Army Corps and the 22nd Army Corps failed to achieve their objectives, Radkevich's 3rd Siberian Army Corps succeeded in occupying Augustów and cutting off German communications. On 16 and 17 September 1914, the 10th Army turned the front to the left, and Radkevich's fought stubbornly in battles near Augustów while other army corps also went over to the offensive and cleared the Augustów Forest of German forces. The 10th Army took about 3,000 prisoners and captured 20 guns. For his performance in these operations, Radkevich was awarded the Order of Saint George Fourth Class.