In the aftermath of World War II, Prussia—a centuries-old state pivotal to Europe's development—ceased to exist. In their eagerness to erase all traces of the Third Reich from the earth, the Allies believed that Prussia, the very embodiment of German militarism, had to be abolished. But as Christopher Clark reveals in this pioneering history, Prussia's legacy is far more complex. What we find is a kingdom that existed nearly half a millennium ago as a patchwork of territorial fragments, with neither significant resources nor a coherent culture. With its capital in Berlin, Prussia grew from being a small, poor, disregarded medieval state into one of the most vigorous and powerful nations in Europe. Iron Kingdom traces Prussia's involvement in the continent's foundational religious and political conflagrations: from the devastations of the Thirty Years War through centuries of political machinations to the dissolution of the Holy Roman Empire, from the enlightenment of Frederick the Great to the destructive conquests of Napoleon, and from the "iron and blood" policies of Bismarck to the creation of the German Empire in 1871, and all that implied for the tumultuous twentieth century.