Question: During what war did Herbert Melhorn serve as director of Stiftung Nordhav, an organization formed by Reinhard Heydrich, who was also a main architect of the Holocaust?

Context paragraphs:
Service record of Reinhard Heydrich: The service record of Reinhard Heydrich was a collection of official SS documents maintained at the SS Personnel Main Office in Berlin from 1934 until the fall of Nazi Germany in 1945.  Most of Reinhard Heydrich's record was captured by the Allies and used for subsequent investigation into Heydrich's duties as head of the RSHA and overall performance in the SS in general.

Dramatic portrayals of Reinhard Heydrich: Dramatic portrayals of Reinhard Heydrich number among the more numerous of any Second World War figure, comparable to Adolf Hitler as well as war films depicting Erwin Rommel.  Reinhard Heydrich has been portrayed in both television and film, and was one of the few high ranking Nazis to be depicted in a dramatic film while the Second World War was still ongoing.

Herbert Mehlhorn: Georg Herbert Mehlhorn (24 March 1903 – 30 October 1968) was an SS "Oberführer", Nazi legal expert, and Gestapo official.  Mehlhorn was involved in the camouflage of the mass graves of the Jewish victims in the forest of the Chełmno extermination camp.  He operated gas wagons at the Chełmno camp to murder the sick Jewish prisoners who were sent from the Wartheland ghettoes.  He was also a director of Stiftung Nordhav, a front organization of the Sicherheitsdienst founded in 1939 by Reinhard Heydrich, one of the main architects of the Holocaust.  He was the mentor of SS-"Brigadeführer" Walter Schellenberg while at the "SS-Hauptamt".

Wannsee Conference: The Wannsee Conference (German: "Wannseekonferenz" ) was a meeting of senior government officials of Nazi Germany and "Schutzstaffel" (SS) leaders, held in the Berlin suburb of Wannsee on 20 January 1942.  The purpose of the conference, called by the director of the Reich Main Security Office SS-"Obergruppenführer" Reinhard Heydrich, was to ensure the cooperation of administrative leaders of various government departments in the implementation of the so-called Final solution to the Jewish question, whereby most of the Jews of German-occupied Europe would be deported to Poland and murdered.  Conference attendees included representatives from several government ministries, including state secretaries from the Foreign Office, the justice, interior, and state ministries, and representatives from the SS.  In the course of the meeting, Heydrich outlined how European Jews would be rounded up and sent to extermination camps in the General Government (the occupied part of Poland), where they would be killed.

Operation Anthropoid: Operation Anthropoid was the code name for the assassination of Schutzstaffel (SS)-"Obergruppenführer" and "General der Polizei" Reinhard Heydrich, head of the "Reichssicherheitshauptamt" (Reich Main Security Office, RSHA), the combined security services of Nazi Germany, and acting "Reichsprotektor" of the Protectorate of Bohemia and Moravia.  The operation was carried out in Prague on 27 May 1942 after having been prepared by the British Special Operations Executive with the approval of the Czechoslovak government-in-exile.  Wounded in the attack, Heydrich died of his injuries on 4 June 1942.  His death led to a wave of merciless reprisals by German SS troops, including the destruction of villages and the killing of civilians.  Anthropoid was the only successful assassination of a senior Nazi leader during World War II.

Heinz Heydrich: Heinz Siegfried Heydrich (29 September 1905 – 19 November 1944) was the son of Richard Bruno Heydrich and the younger brother of SS-Obergruppenführer Reinhard Heydrich.  After the death of his brother, Heinz Heydrich helped Jews escape the Holocaust.

Sicherheitsdienst: Sicherheitsdienst (] , "Security Service"), full title Sicherheitsdienst des Reichsführers-SS (English: Security Service of the Reichsführer-SS ), or SD, was the intelligence agency of the SS and the Nazi Party in Nazi Germany.  The organization was the first Nazi Party intelligence organization to be established and was considered a sister organization with the Gestapo , which the SS had infiltrated heavily after 1934.  Between 1933 and 1939, the SD was administered as an independent SS office, after which it was transferred to the authority of the Reich Main Security Office ("Reichssicherheitshauptamt "; RSHA), as one of its seven departments/offices.  Its first director, Reinhard Heydrich , intended for the SD to bring every single individual within the Third Reich's reach under "continuous supervision."

Stiftung Nordhav: The Stiftung Nordhav ("Nordhav-Stiftung" or Nordhav Foundation) was a front organization of the "Sicherheitsdienst" (SD) founded in 1939 by Reinhard Heydrich to obtain and manage real estate for the SS.

Reinhard Heydrich: Reinhard Tristan Eugen Heydrich (] ) (7 March 1904 – 4 June 1942) was a high-ranking German Nazi official during World War II, and a main architect of the Holocaust.  He was an SS-"Obergruppenführer und General der Polizei" (Senior Group Leader and General of Police) as well as chief of the Reich Main Security Office (including the Gestapo, Kripo, and SD).  He was also "Stellvertretender Reichsprotektor" (Deputy/Acting Reich-Protector) of Bohemia and Moravia.  Heydrich served as president of the International Criminal Police Commission (ICPC; later known as Interpol) and chaired the January 1942 Wannsee Conference, which formalised plans for the Final Solution to the Jewish Question—the deportation and genocide of all Jews in German-occupied Europe.

Richard Bruno Heydrich: Richard Bruno Heydrich (23 February 1865 – 24 August 1938) was a German opera singer (tenor), and composer.  He was the father of SS Obergruppenführer and creator of the Final Solution Reinhard Heydrich, Heinz Heydrich and Maria Heydrich.

Supporting paragraphs: Herbert Mehlhorn Reinhard Heydrich
Answer: World War II