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.

In October and November 1914, the 10th Army fought local battles without any connection with the main operations on the Eastern Front.
In early December 1914, the 10th Army launched a new offensive, but could not break through the fortified front of the German 8th Army and suffered heavy losses.
In early January 1915, the 10th Army conducted the Lasdenen operation, which did not bring the success the Imperial Russian Army expected of it.

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 Elk–Raigorod 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
expressed admiration for Radkevich's actions.

After the German defeat of the 10th Army in the Second Battle of the Masurian Lakes, Radkevich relieved Thadeus von Sivers as commander of the 10th Army on 25 April 1915.
According to the Russian military historian A. A. Kersnovsky in History of the Russian Army, “An excellent corps commander, General Radkevich felt insecure at the head of the army and needed a mentor.”
Radkevich commanded the 10th Army during the Battle of Vilna in August–September 1915, the Sventiany Offensive in September–October 1915, the Lake Naroch Offensive in March 1916, and the Baranovichi Offensive in July 1916.
On 4 October 1916, Radkevich was appointed a member of the Military Council of the Russian Empire.
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.
In October and November 1914, the 10th Army fought local battles without any connection with the main operations on the Eastern Front. In early December 1914, the 10th Army launched a new offensive, but could not break through the fortified front of the German 8th Army and suffered heavy losses. In early January 1915, the 10th Army conducted the Lasdenen operation, which did not bring the success the Imperial Russian Army expected of it.
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 Elk–Raigorod 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
expressed admiration for Radkevich's actions.
After the German defeat of the 10th Army in the Second Battle of the Masurian Lakes, Radkevich relieved Thadeus von Sivers as commander of the 10th Army on 25 April 1915. According to the Russian military historian A. A. Kersnovsky in History of the Russian Army, “An excellent corps commander, General Radkevich felt insecure at the head of the army and needed a mentor.” Radkevich commanded the 10th Army during the Battle of Vilna in August–September 1915, the Sventiany Offensive in September–October 1915, the Lake Naroch Offensive in March 1916, and the Baranovichi Offensive in July 1916. On 4 October 1916, Radkevich was appointed a member of the Military Council of the Russian Empire.
Evgeny Aleksandrovich Radkevich