In the summer of 1870, Napoleon III desperately withdrew his troops from the stronghold where they had been staving off Italian patriots from the greatest prize of the drive for unification, the city of Rome. Bismarck’s armies were sweeping west, a thrust which would end in the Hall of Mirrors at Versailles. This Franco-Prussian War also emptied the Roman Catholic bishops out of St. Peter’s Basilica where they had been meeting since the previous December at the First Vatican Council.
The parents of most of the Council fathers were born in the decades before the French Revolution. The sons grew up during the Age of Metternich when the firemen of Europe, the Concert Powers, tried to stamp out the embers of the Revolution. Many of these men had just been ordained, a few already wore episcopal mitres when most of Europe exploded in 1848. As they assumed leadership in the Church, Garibaldi and Cavour were evicting Pope Pius IX from most of the Papal States.