The papacy of Pius IX lasted 31 years, making it the longest in the history of the Church.

This was a period of political upheaval in Italy. The Church saw its territory slipping away, leaving only the Vatican under papal control.

Pius never again set foot outside the Vatican, and regarded himself as a prisoner. Faced with this loss of temporal power, he sought to underline his spiritual authority.

He called a general council (the First Vatican Council) which produced the decree of papal infallibility. On all issues relating to faith and morals, the pope's word was to be final.

After his death, a Roman mob attempted to throw his body into the River Tiber. But Pius IX is credited with re-inventing the papacy for a modern age.