From 1941, all the German forces on the Eastern Front were organized into three Army Groups, which were to conduct Unternehmen Barbarossa; this military operation was the invasion of the Soviet Union, which started on June 22, 1941. They were Army Group North (Heeresgruppe Nord), Army Group Center (Heeresgruppe Mitte), and Army Group South (Heeresgruppe Süd); they were under direct orders from the German Army High Command (Oberkommando des Heeres). By 1942, around 3,600,000 German soldiers and 6,200 tanks and armoured vehicles of types had been deployed on the Eastern Front by the Wehrmacht, with the German armies being reorganized and reinforced as the war raged on.
The three German army groups on the Eastern Front
Army Group North was led by Field Marshal Wilhelm Ritter von Leeb. It was composed of the 16th and 18th Armies, reinforced by Panzer Group 4th and the Spanish Blue Division. Based in East Prussia, it attacked the Soviet Union, invading the Baltic states of Lithuania, Latvia, and Estonia, securing Army Group Center’s left flank as it pushed eastward. It took part in the Siege of Leningrad.
Under the command of Field Marshal Fedor von Bock, Army Group Center was the strongest one, being composed of the 9th Army and the 4th Army, which were regular field armies, and the 2nd and 3rd Panzer Groups; it successfully took part in the battles of Bialystok-Minsk and Smolensk, but it was defeated at the Battle of Moscow. In 1944, Army Group Center would be smashed during a Soviet counteroffensive called Operation Bagration.
Commanded by Field Marshal Gerd von Rundstedt, Army Group South was made up of the 6th, 11th, and 17th Armies, reinforced by the 1st Panzer Group and the Romanian 3rd and 4th Armies. It participated in the battles of Uman and Kiev. In 1942, Army Group South was reorganized and split into Army Groups A and B. The former took part in the Battle of the Caucasus in Operation Fall Blau, while the latter fought in the Battle of Stalingrad, where the 6th Army, under von Paulus, was totally destroyed.
A German armoured division on the Eastern Front during Operation Barbarossa