 Complete the following phrase:  Hartmann became one of only 27 German soldiers in World War II to receive the Diamonds to his Knights Cross. Hartmann was summoned to the Führerhauptquartier Wolfsschanze, Adolf Hitlers 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 