Karl Decker was born on 30 November 1897 as son to an officer in Borntin in Pomerania. He joined the military service on 3 August 1914 and first saw action in East Prussia. He was promoted to an officer candidate for bravery before the enemy and also was awarded the Iron Cross 2nd Class. Decker was again promoted in 1915 to Leutnant and shortly afterwards received the Iron Cross 1st Class. That same year, he fought in Poland, Russia and Courland He then served as Zugführer of a machine gun unit after he was transferred to the Feldkriegsschule of the German 8th Army in 1916. He was transferred to the Western Front in the spring of 1917 and fought in the Battle of Lys where his division suffered heavy casualties. He then held the position of battalion adjutant. During 1918, he was assigned to the Infantry School in Döberitz as a weapons instructor. After the capitulation of the German Empire, Decker was accepted into the Reichswehr in 1920 and served with the 29th Reserve Jäger Regiment, the 5thJäger Regiment and the 6th cavalry Regiment. He was promoted to Oberleutnant and Rittmeister during these assignments. As a major, he was transferred to the staff of the 5th Cavalry Regiment together with Horst Niemack. Shortly afterwards, he was reassigned again, this time to the 38th Armoured Detachment in Mühlhausen. He later became the commanding officer of this unit. This unit was subordinated to the 2nd Panzer division during the Invasion of Poland and fought under the command of Decker near Kraków and the Jablonka Pass. During the Battle of France, Decker commanded a battalion of the 3rd Panzer regiment in the 2nd Panzer division. This unit fought at the Maas, near Sedan, St. Quentin and Abbeville. In Balkans Campaign, his regiment fought in Yugoslavia, northern Greece, occupied Athens and crossed the Corinth Canal. Decker was put in command of 3rd Panzer regiment before Operation Barbarossa began. In the spring of 1942, he was transferred to the staff of the 9th Army. In April 1943, he appointed commander of the 5th Panzer Division. He received the Oak Leaves to the Knight's Cross on 4 May 1944 and promoted to Generalleutnant. Decker was appointed commander of the XXXIX Panzer Corps that was attached to the 3rd Panzer Army and promoted to General der Panzertruppe on 1 January 1945. After his unit was relocated to the Western Front, his corps fought the Americans at Uelzen and in the Alsace. Here the 5th Panzer Army was subordinated to Army Group B. Decker committed suicide on 21 April 1945 after the defeat and encirclement of the Army Group in the Ruhr Pocket in April.
