Otto von Bismarck's leadership refers to his role as the Chancellor of Germany from 1867 to 1870 and then from 1871 to 1890, where he was instrumental in unifying Germany and shaping its political landscape. His pragmatic approach, known as Realpolitik, emphasized practical solutions over ideological considerations, allowing him to navigate complex European politics, engage in wars that expanded German territory, and maintain stability through a series of alliances.