How Did Bismarck Unify Germany Through War and Compromise?

Geoffrey Chen

The Making of the Modern World: Thirty Lectures on Nineteenth-Century European History · Article 17

In January 1871, German princes gathered in the Hall of Mirrors at Versailles and acclaimed King Wilhelm I of Prussia as German emperor. The scene appears to confirm the simplest version of Otto von Bismarck’s politics of ‘iron and blood’: wars defeated Germany’s external enemies, and Prussia unified the nation. Yet armies alone did not create the empire. Unification also depended on economic links formed through the customs union, nationalist public opinion, parliamentary approval, negotiations with sovereign princes and peace terms designed, at crucial moments, to preserve future cooperation. Bismarck’s distinctive skill was not merely starting wars. It was limiting some of them, stopping when his political objective had been reached, and converting victory into institutions that relevant parties could accept without necessarily welcoming.

That qualification matters because neither a cult of Bismarck’s genius nor a tale of inevitable national awakening explains the outcome. Germany had several imaginable borders and constitutions. Prussia possessed formidable resources but faced domestic opposition. Austria remained a major German power, and the southern kingdoms guarded their independence. Bismarck unified Germany through war because force altered these constraints. He unified it through compromise because force could not by itself make a stable federation.

1848 left an objective and exposed the divisions

After the Holy Roman Empire ended in 1806, ‘Germany’ still comprised numerous sovereign states. The German Confederation created in 1815 was chaired by Austria, with Prussia as its principal rival. A shared written language, cultural nationalism, university associations and the expanding Zollverein customs union strengthened connections across borders. None answered the decisive political questions: who should govern, which territories belonged, and how much sovereignty should the member states surrender? The choice between a ‘Greater Germany’ including Austria and a ‘Lesser Germany’ excluding it was also a question about whether the Habsburg monarchy, with its many non-German peoples, could fit within a national state.

The Frankfurt National Assembly of 1848 attempted to create unity through representation and constitutional deliberation. After prolonged debate, its members offered a hereditary imperial crown to King Friedrich Wilhelm IV of Prussia. He refused. The revolution’s failure did not make liberal nationalism irrelevant. Frankfurt clarified a Lesser German option, articulated fundamental rights and made a national parliament imaginable. It failed for several reasons: revolutionaries divided over social and territorial issues, the assembly lacked an independent army, monarchies recovered their authority, and the international setting was unfavourable. Bismarck inherited its national question but shifted the location of effective choice. Instead of a national assembly designing a state and asking a monarch to accept it, the Prussian government would change the balance of power and then ask representatives to ratify much of the result.

Constitutional conflict formed the setting for ‘iron and blood’

Wilhelm I appointed Bismarck minister-president in 1862 during a confrontation with the Prussian parliament over funds for army reform. Bismarck argued that the government could continue collecting taxes because the constitution did not specify how to resolve a deadlock. His famous speech about the great questions of the day being decided by iron and blood was a polemical defence of state power, not a detailed blueprint for three future wars. Liberal deputies feared that the executive was placing army and bureaucracy beyond parliamentary control. Bismarck used the existing administration to proceed without an approved budget.

This conflict shows that unification was never simply a national campaign against outsiders. Prussians first disputed who controlled the resources of their own state. Military reform helped provide the capacity for subsequent victories, but it created a profound problem of legality. After defeating Austria in 1866, Bismarck did not permanently crush the parliamentary liberals. He requested an Indemnity Bill retrospectively approving the unbudgeted expenditure. Many National Liberals accepted the settlement because national success seemed to vindicate the government’s course. The compromise divided liberalism: some maintained that constitutional principle had been surrendered, while others expected cooperation to produce legal unity and further reform.

War with Denmark made rivals into temporary allies

The duchies of Schleswig and Holstein had long possessed intricate dynastic and constitutional relationships with the Danish crown and the German Confederation. Denmark’s attempt in 1863 to bind Schleswig more closely to the kingdom provoked German nationalist outrage. Bismarck prevented smaller German governments or nationalist associations from controlling the dispute. He invoked the language of international treaties and brought Prussia and Austria together in war against Denmark. Defeated in 1864, Denmark ceded both duchies.

The campaign generated genuine national enthusiasm, but its political importance lay in the problem created by victory. Prussia and Austria now had to administer their acquisitions together. Bismarck did not invent their rivalry, the constitutional dispute or every step towards conflict. He did, however, narrow the diplomatic alternatives. Prussia could appear to defend treaty rights and German interests while Austria entered a partnership that would be hard to sustain. The first war was simultaneously a national cause and a calculated move that created the setting for a new German balance of power.

In 1866, limited peace excluded Austria

Disputes over administration of the duchies escalated in 1866. Bismarck secured an Italian alliance and worked to reduce the likelihood of Russian or French intervention. Prussia moved outside the confederal framework and fought Austria and its German allies. Training, railway mobilisation, General Staff planning and the needle gun all contributed to Prussian performance, but technological superiority did not make victory automatic. The Seven Weeks’ War was decided after the major battle of Königgrätz, or Sadowa. Prussia annexed Hanover and several other northern states, while the old German Confederation disappeared.

The restraint imposed after the battle was as consequential as the battle itself. Wilhelm and some commanders wanted to march towards Vienna. Bismarck opposed humiliating Austria. His objective was to remove it from German affairs, not to create an irreconcilable enemy or endanger the Habsburg monarchy. The Peace of Prague took no Austrian core territory. This moderation preserved the possibility of later cooperation, even as it confirmed Prussia’s German predominance.

The North German Confederation established in 1867 turned victory into a constitutional order. It had a Bundesrat representing state governments and a Reichstag elected by universal adult male suffrage. The Prussian king held the federal presidency, Bismarck served as chancellor, and the army remained central. Universal male suffrage was strikingly broad by contemporary standards and gave national politics a popular arena. It did not create parliamentary government: the chancellor did not depend on the confidence of a Reichstag majority. Liberal legislation and monarchical executive power consequently developed side by side.

The French war joined north and south, but was no one-man plot

The Catholic states south of the River Main remained formally independent, although they had secret military agreements with Prussia. In 1870 a Hohenzollern candidacy for the Spanish throne produced a Franco-Prussian crisis. Bismarck edited the report of the Ems meeting before publication, making the firm positions of both courts appear more provocative. Napoleon III’s government declared war. Bismarck deliberately exploited the crisis, but the claim that he alone scripted every event exaggerates his control and obscures French domestic pressures, dynastic politics and years of mutual suspicion.

France’s declaration allowed the southern states to fight in what could be represented as a defensive German war. German forces won rapidly, capturing Napoleon III at Sedan and precipitating the fall of the Second Empire. The conflict did not end with that regime. It continued against the new French Republic, and Paris endured a long siege. National consolidation and escalating violence were parts of the same process.

The peace settlement annexed Alsace and part of Lorraine and imposed a large indemnity. It transferred inhabitants without a meaningful choice and burdened Franco-German relations. Unlike the restraint shown towards Austria in 1866, the French settlement created a durable grievance.

The empire was a negotiated federal monarchy

Southern entry did not follow automatically from victory. Bavaria, Württemberg, Baden and Hesse negotiated over military arrangements, taxation, post and reserved rights. Bismarck also encouraged King Ludwig II of Bavaria to invite Wilhelm to accept the imperial title, making the crown appear to come from Germany’s princes. Even the wording mattered. An ‘emperor of the Germans’ could imply popular sovereignty; ‘German emperor’ better preserved the standing of the other monarchs.

The constitution of 1871 largely extended that of the North German Confederation. The Bundesrat represented governments, while the Reichstag was elected by adult men. The empire gained authority over foreign policy, armed forces, customs and significant areas of law. The Reichstag legislated and voted budgets, but it could not dismiss the chancellor by a parliamentary vote of no confidence. Prussia dominated in territory, population and military power, and its king was the emperor. Yet states retained governments and meaningful rights, particularly in areas such as education and religion.

The resulting polity was neither a unitary Prussian conquest nor a liberal parliamentary nation-state. It was a compound of national institutions, federal bargains and dynastic hierarchy. Its durability came partly from this ambiguity. Liberals could value elections, economic integration and common law; princes could retain thrones; conservatives could rely on the imperial executive; many workers would later use elections to build a mass socialist party. No group received everything, but several acquired reasons to participate.

Connection to intellectual history: did success justify the means?

Bismarck is commonly associated with Realpolitik: attention to power, interest and the possible rather than obedience to an abstract scheme. Realpolitik did not mean the absence of conviction or limitless cynicism. Bismarck was a conservative monarchist who opposed the popular sovereignty of 1848. He nevertheless used nationalism, universal male suffrage and constitutional forms because they could strengthen the state he served. National Liberals cooperated because they expected national and legal integration to enlarge freedom. That cooperation changed liberalism itself. One branch moved from opposition to dynastic authority towards participation in state-building.

Victory tempts retrospective moral reasoning. Military success could make the unapproved budgets of the 1860s appear lawful in spirit, or make the eventual empire seem to validate every diplomatic manipulation. It did neither. Nor did unification cancel the experience of French civilians under siege, soldiers killed in three wars, Danes separated from their state, or inhabitants of annexed Alsace-Lorraine. Outcomes are evidence of capacity, not automatic proof of justice.

The opposite deterministic judgement is also unsound: the empire of 1871 was not inevitably the first stage on a fixed road to twentieth-century catastrophe. Its constitution did leave the executive and army unusually independent of parliament, and Prussian dominance shaped political culture. It also created competitive elections, federal negotiation, public law and social movements whose futures were open. Institutions constrained later choices without dictating them.

Bismarck unified Germany through war because Prussian force resolved territorial and constitutional questions that speeches had not settled. He unified it through compromise because battlefield victory could not itself reconcile liberals, preserve useful relations with Austria, secure the southern governments or clothe Prussian predominance in federal legitimacy. The answer lies in the combination: calculated violence changed the bargaining position, and selective restraint made a settlement possible. The empire was not the pure embodiment of a national will. It was a Prussian-led federation built by altering political facts through war and then fixing them through law, consent and concession. That was a remarkable political achievement, but achievement alone cannot turn its methods into moral necessity.

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