 Sixtus arrived with conditions for talks which had been agreed with the French — the restoration to France of Alsace @-@ Lorraine ( annexed by Germany after the Franco @-@ Prussian War in 1870 ) ; restoration of the independence of Belgium ; independence for the kingdom of Serbia ; and the handover of Constantinople to Russia . Charles agreed , in principle , to the first three points and wrote a letter to Sixtus dated 25 March 1917 which sent " the secret and unofficial message " to the President of France that " I will use all means and all my personal influence " . This attempt at dynastic diplomacy eventually foundered . Germany refused to negotiate over Alsace @-@ Lorraine , and , seeing a Russian collapse on the horizon , was loath to give up the war . Sixtus continued his efforts , even meeting Lloyd George in London about Italy 's territorial demands on Austria in the Treaty of London of 1915 , but the Prime Minister could not persuade his generals that Britain should make peace with Austria . Zita managed a personal achievement during this time by stopping the German plans to send airplanes to bomb the home of the King and Queen of Belgium on their name days . 
