After the general mobilisation in August 1939 IX Corps were stationed near Worms as 1st Army reserves.

In May 1940 they took part in Fall Gelb, the Manstein plan to invade the Low Countries and France via the Ardennes, pushing on to Dunkirk.

Transferred to the Eastern Front in 1941 to take part in Operation Barbarossa, the invasion of the Soviet Union, the corps, at that time consisting of 137th, 263rd and the 292nd Infantry Division, were transferred to the 4th Army under the overall command of Field Marshal Günther von Kluge.

They reached the Dnieper river where they encountered strong Soviet resistance and by the end of 1942 had to fall back.

By 1945 the corps had fallen back to the Deyma River near Kaliningrad, where they established a defensive position.