 In 1908 , Pacelli served as a Vatican representative on the International Eucharistic Congress , accompanying Rafael Merry del Val to London , where he met Winston Churchill . In 1911 , he represented the Holy See at the coronation of King George V. Pacelli became the under @-@ secretary in 1911 , adjunct @-@ secretary in 1912 ( a position he received under Pope Pius X and retained under Pope Benedict XV ) , and secretary of the Department of Extraordinary Ecclesiastical Affairs in February 1914 . On 24 June 1914 , just four days before Archduke Franz Ferdinand of Austria was assassinated in Sarajevo , Pacelli , together with Cardinal Merry del Val , represented the Vatican when the Serbian Concordat was signed . Serbia 's success in the First Balkan War against Turkey in 1912 had increased the number of Catholics within greater Serbia . At this time Serbia , encouraged by Russia , was challenging Austria @-@ Hungary 's sphere of influence throughout the Balkans . Pius X died on 20 August 1914 . His successor Benedict XV named Gasparri as secretary of state and Gasparri took Pacelli with him into the Secretariat of State , making him undersecretary . During World War I , Pacelli maintained the Vatican 's registry of prisoners of war and worked to implement papal relief initiatives . In 1915 , he travelled to Vienna to assist Monsignor Raffaele <unk> , nuncio to Vienna , in his negotiations with Emperor Franz Joseph I of Austria regarding Italy . 
