 By the spring of 1917 , the War was dragging on towards its fourth year , and Zita 's brother Sixtus of Bourbon @-@ Parma , a serving officer in the Belgian Army , was a main mover behind a plan for Austria @-@ Hungary to make a separate peace with France . Charles initiated contact with Sixtus through contacts in neutral Switzerland , and Zita wrote a letter inviting him to Vienna . Zita 's mother Maria Antonia delivered the letter in person . 
