In von Einem's term of office as Minister of War, 1903-09, he introduced the use of the machine gun in the German army and reinforced the heavy artillery in preparation for modern war. but he declined the addition to the army. In 1909 v. Einem became General of the VII. Corps, which during the Great War was a part of the 2. Army under von Bülow.
After Ludendorff and v. Emmich seized the town of Liege, v. Einem was given commnd of the besieging units against the forts of Liège (August 8. 1914). The VII. Corps was the corps on the right wing of the 2. Army, directly on the gap to the 1. Army (v. Kluck). On September 12.1914 v. Einem became commander-in-chief of the 3. Army, succeeding General Max von Hausen. The frontline of his army were positioned on the line between Reims and the Argonne in the Champagne. Here, the army beat back the French attempts at breakthrough in the winter and autumn of 1915 and in 1917, but his forces lost badly when faced by General Pershing's AEF during the Meuse-Argonne offensive, and Einem was forced to retreat north. V. Einem's army took part in the last German attack in July 1918 on both sides of Reims.
After the Armistice, v. Einem returned the Army Group German Crown Prince to Germany.
Einem, Karl v., Ein Armeeführer erlebt den Weltkrieg, Leipzig: Koehler, 1933
Einem, Karl v., Erinnerungen eines Soldaten, Leipzig: Koehler, 1933
Gackenholz, Hermann, in Neue Deutsche Biographie, Bd. 4
Der Weltkrieg 1914-18, bearb. im Reichsarchiv, Berlin