With the outbreak of World War I Wangenheim was instrumental in securing the entry of the Ottoman Empire into the war as part of the Central Powers. Wangenheim oversaw Max von Oppenheim's successful attempt to get the Ottoman Caliph Mehmed V to declare Jihad against the Triple Entente.[2] During the time of Armenian Genocide there were accusations of German complicity and question's were raised as to Wangenheim's position of 'non-intervention'; the American Ambassador to the Ottoman Empire Henry Morgenthau in his book Ambassador Morgenthau's Story (1918) would virulently criticise Wangenheim's role.[3] In an interview with an American journalist, Wangenheim stated: "I do not blame the Turks for what they are doing to the Armenians...They are entirely justified".[4]