'Blood and Iron' refers to a famous speech made by Otto von Bismarck in 1862, which emphasized the importance of military strength and industrial power in achieving German unification. This speech highlighted Bismarck's belief that realpolitik and the use of force, rather than diplomacy or ideals, were necessary to unify the German states. The phrase encapsulates Bismarck's pragmatic approach to politics and his commitment to strengthening Prussia as a means to lead the way toward a unified Germany amidst rising tensions in Europe.