After the withdrawal of a French garrison, Italian troops entered Rome, turning this pope into a "prisoner in the Vatican."
Karl Kajetan von Gaisruck ("KYE-tahn fon GUYS-rook") arrived at a meeting too late to exercise his right to exclude this person from coming to power. This leader's government abducted a six-year-old Jewish boy after it had discovered that he had been baptized; that boy was Edgardo Mortara. This pope, who unilaterally rejected the Law of Guarantees, promulgated the encyclical (*) Quanta cura, to which a document listing eighty "principal errors of our times" was attached; that document was the Syllabus of Errors. After the withdrawal of a French garrison, Italian troops entered Rome, turning this pope into a "prisoner in the Vatican." For 10 points, name this pope who defined the Immaculate Conception and convened the First Vatican Council, which defined papal infallibility.
Karl Kajetan von Gaisruck ("KYE-tahn fon GUYS-rook") arrived at a meeting too late to exercise his right to exclude this person from coming to power.
Pius IX [or Giovanni Maria Mastai-Ferretti]