In the latest National Review, Ross Douthat reviews Michael Burleigh's Earthly Powers: The Clash of Religion and Politics in Europe from the French Revolution to the Great War :
There is a tendency to view the European 19th century as a period of vanished tranquility — a hundred years of peace, optimism, and progress between the chaos of the French Revolution and the charnel house of World War I. Burleigh’s book is an antidote to such nostalgia, and a reminder that the 1800s were the period when the ideas unleashed in 1789 — the enthronement of political religion, in particular, and the deification of the nation and the state — worked themselves deep into the soil of continental politics, whence the poisoned fruit of 20th-century totalitarianism would spring.
Reading Earthly Powers will make any Catholic thankful for the likes of Benedict XVI and John Paul II — as opposed to the succession of 19th-century Popes who clung, hopelessly but doggedly, to temporal power and a throne-and-altar world gone by. With the honorable exception of Leo XIII, who did much to reconcile the Church to the realities of democracy and the industrial age, the occupants of the see of Peter were either pious incompetents like Gregory XVI — “motionless in the thick darkness that surrounds him,” Lamennais wrote, “he weeps and prays” — or stiff-necked blunderers like Pius IX, who lost the Papal States and penned the Syllabus of Errors, a document whose prescient warnings about nationalism were lost amid a cascade of venom. (“Rhetorical moderation, sensitivity, and subtlety were alien to him,” Burleigh remarks.)
Many of the Protestant churches were, if anything, even worse — less nostalgic than the Holy See for a vanished age of absolutism, but more vulnerable to the siren song of ideologies that promised heaven on earth, or substituted the nation-state for God. In Germany, in particular, the Protestant willingness to uncritically embrace Teutonic nationalism anticipated the tragedies of the following century. The “Hegelian strain in liberal Protestant theology,” Burleigh points out, “in which whatever one felt powerfully enough was indicative of the developing presence of God,” lent itself easily to the deification of nationalist enthusiasms — culminating in August 1914, when a German pastor could argue unselfconsciously that “God is what the god-inspired people do.”