In the summer of 1862, Otto von Bismarck was appointed minister-president of Prussia. His highest previous rank had been ambassador to Russia. He had never held an administrative position. Yet with a few brusque strokes, the novice minister solved the riddle that had stymied European diplomacy for two generations: how to unify Germany and reorganize Central Europe. He had to overcome the obstacle that Germany comprised 39 sovereign states grouped in the so-called German Confederation. All the while, Central European trends were warily observed by the two “flanking” powers, France and Russia, ever uneasy about — and tempted to prevent — the emergence of a state capable of altering the existing European balance of power.

Within nine years, Bismarck untied this knot in what Jonathan Steinberg, a professor of history at the University of Pennsylvania, describes as “the greatest diplomatic and political achievement by any leader in the last two centuries.” He overcame the princes of the German states in two wars and rallied them in a third; won over public opinion by granting universal manhood suffrage — making Prussia one of the first states in Europe to do so; paralyzed France by holding out the prospect of agreeing to the French acquisition of Luxembourg, and Russia by a benevolent attitude during the Polish revolution of 1863. Bismarck accomplished all this “without commanding a single soldier, without dominating a vast parliamentary majority, without the support of a mass movement, without any previous experience in government and in the face of national revulsion at his name and his reputation.”

It is a measure of Steinberg’s achievement in “Bismarck: A Life” that the subsequent description of the “political genius of a very unusual kind” becomes far from a panegyric. He describes — in an incisive, if occasionally distracting, psychological approach — a highly complex person who incarnated the duality that later tempted Germany into efforts beyond its capacity. Bismarck was never seen in public without a uniform, yet he had never really served in the military and was generally viewed with suspicion by the military leaders for what they saw as his excessive moderation. The man of “blood and iron” wrote prose of extraordinary directness and lucidity, comparable in distinctiveness to Churchill’s use of the English language. The embodiment of ­realpolitik turned power into an instrument of self-restraint by the agility of his diplomacy. He dominated Germany and European diplomacy from a single power base, the confidence of an aging king, without other institutional backing or great personal following.