He was drafted as a field hospital inspector and served from 1914 to 1917 on the front lines in Flanders, Romania and the Baltic States, earning the Iron Cross, 2nd class.

After the outbreak of the Second World War, Telschow served as a member of the Defense Committee for Wehrkreis (Military District) XI from 22 September 1939.

One of the older Gauleiters, and not particularly ambitious or capable, Telschow often turned over the day-to-day running of his Gau to his Deputy, Heinrich Peper.

[8] In the postwar memoir by Albert Krebs, the former Gauleiter of Hamburg, Telschow was characterized in this way: On his frequent visits to our headquarters, we usually tried to compliment him out the door as quickly as possible because he kept us from working and also had nothing particularly clever to contribute to a conversation ... a man of undoubtedly honest intentions but not equipped with any noteworthy abilities … he knew nothing about the interconnections, background, and effective forces of politics or history.

An investigation by Walter Buch’s Oberste Parteigericht (Supreme Party Court) recommended the opening of formal proceedings against him.

However, in December 1941, this was quashed due to the intervention of Martin Bormann who was familiar with Hitler's reluctance to discipline or remove any Alter Kämpfer (old fighter) that had been with him from the earliest days.

In this capacity, he had jurisdiction over civil defense and evacuation measures, as well as control over the war economy, including rationing and suppression of black market activities.

[11] Toward the close of the war, when British troops entered Lüneburg on 18 April 1945, Telschow fled from his villa to a hunting lodge near Dahlenburg.