Küchler continued in the German army after the war, and his service was marked by steady advancement. He was promoted to major in 1924, to lieutenant colonel in 1929, and to full colonel in 1932. By 1934, he was a Generalmajor (U.S. equiv. brigadier general), commanding the 1st Infantry Division in East Prussia. Promoted in 1935 to Generalleutnant (U.S. equiv. major general), Küchler was appointed to the post of inspector general of the service academies.
In April 1937, Küchler was made General der Artillerie (U.S. equiv. lieutenant general), commanding I Army Corps at Königsberg. In March 1939, his forces participated in the incorporation of Memel into the Reich. In the German invasion of Poland, Küchler commanded Third Army, which struck south from East Prussia as part of Colonel General Fedor von Bock's Army Group North. During the Polish Campaign, Küchler directed the northern portion of the envelopment of Warsaw. Although seen as a favorite of Adolf Hitler, Küchler defied Schutzstaffel (SS) leader Heinrich Himmler and ordered the courts-martial of German soldiers guilty of committing atrocities against Poles.
During the invasion of France and the Low Countries in May 1940, Küchler commanded Eighteenth Army, consisting of 11 divisions in Bock's Army Group B. He had responsibility for the invasion of the Netherlands and the linkup with highly vulnerable German airborne forces holding key bridges, cities, and installations. Following the surrender of the Netherlands on 15 May, Küchler's forces occupied Antwerp, then forced the Scheldt and drove on Ghent in Belgium. His forces then mopped up the remaining resistance following the British evacuation at Dunkerque before driving south toward Amiens and taking Paris on 14 June.
Promoted to full general in July 1940, Küchler then led his Eighteenth Army as part of Field Marshal Wilhelm von Leeb's Army Group North in Operation barbarossa, the invasion of the Soviet Union. Eighteenth Army held the north flank in the advance toward Leningrad. In addition to forcing prisoners of war to clear mines, Küchler also enforced Hitler's Commissar Order, and he ordered the execution of both partisans and Gypsies.
In January 1942, Küchler took over command of Army Group North from Leeb. He was promoted to field marshal in June 1942. When the Soviets launched their great counteroffensive at Leningrad on 28 January 1944, Küchler was forced to withdraw to the Luga River. Hitler made him the scapegoat for the reverse, and on 29 January, he temporarily replaced him with Field Marshal Walther Model. On 31 January, Hitler retired him altogether.
Arrested after the war, Küchler was tried and convicted of war crimes at Nuremberg in October 1948 and sentenced to 20 years of imprisonment. Freed in February 1955, he died in Garmisch-Partenkirchen, Germany, on 25 May 1968.
Spencer C. Tucker
Glantz, David M. The Battle for Leningrad, 1941–1944. Lawrence: University Press of Kansas, 2002.; Mitcham, Samuel W., Jr. Hitler's Field Marshals and Their Battles. Chelsea, MI: Scarborough House, 1988.