He served in several SS and Police Leader positions in occupied Ukraine and Italy during the Second World War.

After school, Tensfeld joined the German Imperial Navy in 1909 and was deployed during the First World War with the U-Boat service.

From 1 January 1939 to 1 June 1942 he was Chief of Staff in the SS-Oberabschnitt (Main District) "Northwest" (renamed "Nordsee" in April 1940) based in Altona, Hamburg.

On 19 May 1943, Tensfeld was transferred to succeed SS-Brigadeführer Hans Döring in the post of SSPF "Stalino-Donezgebiet," serving there until 4 September 1943.

[4] Tensfeld was next sent as an SSPF for special assignment under the Supreme SS and Police Leader in Italy, SS-Obergruppenführer Karl Wolff, where he became the German liaison officer to the fascist regime recently established as the Italian Social Republic.