Hartmann became one of only 27 German soldiers in World War II to receive the Diamonds to his Knight's Cross. Hartmann was summoned to the "Führerhauptquartier Wolfsschanze", Adolf Hitler's military headquarters near Rastenburg, to receive the coveted award from Hitler personally. Hartmann was asked to surrender his side arm — a security measure heightened by the aftermath of the failed assassination attempt on 20 July 1944. According to one account, Hartmann refused and threatened to decline the Diamonds if he were not trusted to carry his pistol. During Hartmann's meeting with Hitler, Hartmann discussed at length the shortcomings of fighter pilot training. Allegedly, Hitler admitted to Hartmann that he believed that, "militarily, the war is lost," and that he wished the Luftwaffe had "more like him and Rudel."