A major new account of the post-Napoleonic Holy Alliance and the promise it held for liberalsThe Holy Alliance is now most familiar as a label for conspiratorial reaction. In this book, Isaac Nakhimovsky reveals the Enlightenment origins of this post-Napoleonic initiative, explaining why it was embraced at first by many contemporary liberals as the birth of a federal Europe and the dawning of a peaceful and prosperous age of global progress. Examining how the Holy Alliance could figure as both an idea of progress and an emblem of reaction, Nakhimovsky offers a novel vantage point on the history of federative alternatives to the nation state. The result is a clearer understanding of the recurring appeal of such alternatives—and the reasons why the politics of federation has also come to be associated with entrenched resistance to liberalism’s emancipatory aims. Nakhimovsky connects the history of the Holy Alliance with the better-known transatlantic history of eighteenth-century constitutionalism and nineteenth-century efforts to abolish slavery and war. He also shows how the Holy Alliance was integrated into a variety of liberal narratives of progress. From the League of Nations to the Cold War, historical analogies to the Holy Alliance continued to be drawn throughout the twentieth century, and Nakhimovsky maps how some of the fundamental political problems raised by the Holy Alliance have continued to reappear in new forms under new circumstances. Time will tell whether current assessments of contemporary federal systems seem less implausible to future generations than initial liberal expectations of the Holy Alliance do to us today.