During the German invasion of the Soviet Union, as commander of the 6th Army, he led his army into the heart of Russia during the summer of 1941. The 6th Army was a part of Army Group South, and captured Kiev, Belgorod, Kharkov and Kursk. During its offensive into the Soviet Union, the German army was confronted with a number of superior tank designs. Reichenau inspected the Soviet tanks he came across, entering each tank and measuring its armour plate. According to general staff officer Paul Jordan, after examining a T-34, Reichenau told his officers "If the Russians ever produce it on an assembly line we will have lost the war."