Context : Karl-Heinz Ertel (26 November 1919 -- 25 January 1993) was a SS-Hauptsturmführer of the Reserves, in the Waffen-SS during World War II who was awarded the Knight's Cross of the Iron Cross, to recognize extreme battlefield bravery or successful military leadership by Nazi Germany during World War II. 
Answer : World War II
Which war did Karl-Heinz Ertel participate in?