19 April 1938, he became Commanding Officer of Signals Training, but later took part in the Anschluss. World War II In 1939, Randewig was responsible for three signal intercept companies posted to the West Wall. It was feared by Germany that France would invade Germany, and Randewig's job was to use his intercept companies to detect any movement in the French forces. In August 1939, Randewig was mobilised into the O.C. Signals Operational Abteilung (department) of the Army Advanced Guard. At the time, there were two fixed intercept stations in the west-Stuttgart and Münster. Randewig's next posting was the Signals Interception unit in Zeppelin bunker in Wünsdorf near Zossen, Brandenburg, to intercept signals from Poland. In mid September 1939, he became Commanding Officer Intercept Troops, West and helped to build up the new Army H.Q in Giesen. During this period, his commitments were against France, Belgium and Holland inclusively. In April 1940, the Intercept unit that Randewig was commanding was split into three separate units, to cover Army Group A, B and C. Each had a Commanding Officer (O.C.) of Signals Interception and Randewig was made Commanding Officer of Signal Interception of Army Group A, with General Gerd von Rundstedt as his G.O.C. Working until the end of June, Randewig was working with three intercept companies monitoring French radio communications exclusively. On 1 April 1940, Randewig started studying message interception from radio communications from Great Britain. Facilities available were the fixed intercept station at Husum, the Münster and Euskirchen. They were also two mobile intercept companies together with Direction finding (abbr. D/F) sections. This went on until April 1941. General Rundstedt was then posted to the Eastern Front and Randewig's unit was posted as well. The Army Group became Army Group South. Randewig was promoted to () Lt. Colonel and to () Colonel in 1942. There were three companies engaged in Signals Interception against the Soviets, KONA 1, KONA 2 and KONA 3. In October 1942, Randewig was to become Commander of Signals of the 3rd Romania Army but fell ill. In February–March 1943, he was posted to Führerreserve at Halle. In April Randewig became C.S.C. of Armeeoberkommando 15, in the Netherlands area. In July, Randewig was again posted to the Führerreserve, as a result of indiscreet criticism of the regime. In October 1943, proceedings against him stopped as he was given a warning. In December 1943, he was posted