World War I

On June 28, 1914, a nineteen-year-old Bosnian Serb nationalist named Gavrilo Princip fired two shots in Sarajevo, killing Archduke Franz Ferdinand of Austria-Hungary and his wife Sophie. Within six weeks, the assassination of one man had produced a general European war involving eight nations and their global empires. Within four years, that war had killed approximately 20 million people—9.7 million military personnel and perhaps 10 million civilians—wounded 21 million more, destroyed four empires, redrew the map of Europe and the Middle East, and created conditions that led directly to an even more devastating conflict a generation later.

The war that contemporaries called the “Great War” was the defining catastrophe of the 20th century. It shattered the 19th-century order built at the Congress of Vienna—an order of great power concert, dynastic legitimacy, and European predominance that had prevented major war for a century. In its place emerged unstable democracies, revolutionary ideologies, economic dislocation, and territorial grievances that no settlement could resolve. Understanding World War I is essential for grasping how the modern state system works—and how it fails.

The Long Fuse¶

The Alliance System¶

By 1914, Europe’s great powers had divided into two rival alliance blocs, each originally defensive in purpose but collectively transforming any bilateral dispute into a continental crisis:

The Triple Alliance (1882) bound Germany, Austria-Hungary, and Italy into a mutual defense pact. Germany, unified only since 1871, had become the continent’s premier industrial and military power. Its population had grown from 41 million in 1871 to 65 million in 1914; its steel production surpassed Britain’s; its army was Europe’s largest and best trained. Austria-Hungary, by contrast, was a declining multinational empire struggling to hold together eleven major nationalities. Italy was the alliance’s weakest link, harboring territorial ambitions against Austria-Hungary itself.

The Triple Entente (formalized by 1907) linked France, Russia, and Britain in a looser arrangement. France sought revenge for the humiliation of 1870-1871, when Prussia had defeated it, seized Alsace-Lorraine, and proclaimed the German Empire in the Hall of Mirrors at Versailles. Russia, the world’s largest country by territory, was modernizing rapidly—its population of 170 million and its French-financed industrialization alarmed German planners who saw a closing window of military advantage. Britain, the world’s foremost naval and colonial power, had abandoned its traditional “splendid isolation” in response to Germany’s aggressive naval buildup.

The alliance system’s danger was structural: a crisis between any two members of opposing blocs could drag in all the others. A Balkan quarrel between Austria-Hungary and Serbia could escalate to a Russo-Austrian confrontation, then a German-Russian war, then a Franco-German war, then—if Germany violated Belgian neutrality to outflank France—a British-German war. This is precisely what happened.

Imperial Rivalry and the Arms Race¶

The decades before 1914 saw intensifying competition among the great powers:

Colonial rivalry: The Scramble for Africa (1881-1914) had divided most of Africa among European powers, producing periodic crises—the Fashoda Incident (1898) nearly provoked war between Britain and France; the Moroccan Crises (1905, 1911) brought Germany into confrontation with France and Britain. The Great Game between Britain and Russia for influence in Central Asia added another dimension of tension. By 1914, the globe had been largely divided; further expansion meant taking from rivals rather than claiming unclaimed territory.

Naval arms race: Germany’s decision to build a battle fleet capable of challenging the Royal Navy—embodied in the Naval Laws of 1898 and 1900 and championed by Admiral Alfred von Tirpitz—was perhaps the single most destabilizing policy decision of the pre-war era. Britain, whose security depended on naval supremacy, responded with the revolutionary HMS Dreadnought (1906), rendering all previous battleships obsolete and resetting the competition. By 1914, Britain had 29 dreadnoughts to Germany’s 17, but the race had poisoned Anglo-German relations beyond repair.

Military planning: Europe’s general staffs had prepared war plans of extraordinary rigidity. Germany’s Schlieffen Plan required a rapid invasion of France through Belgium before turning east against Russia—a timetable that left no room for diplomacy once mobilization began. Russia’s mobilization plans were similarly inflexible: once ordered, they could not easily be limited or reversed. The mobilization schedules of 1914 turned a political crisis into a military one, as generals demanded decisions before diplomats had finished talking.

Nationalism and the Balkan Powder Keg¶

Balkans—where Ottoman decline had created a volatile mix of small states, ethnic grievances, and great power ambitions—were the immediate trigger:

The Ottoman Empire’s slow collapse across the 19th century had created Greece, Serbia, Bulgaria, Romania, Montenegro, and Albania—new states often with overlapping territorial claims and aggrieved minorities. Austria-Hungary’s 1908 annexation of Bosnia-Herzegovina infuriated Serbia, which considered the territory’s Serb population part of its national patrimony. Russia backed Serbia as a fellow Slavic state and as a tool for expanding influence in the region. Germany backed Austria-Hungary as its only reliable ally.

Two Balkan Wars (1912-1913) had doubled Serbia’s territory and population, alarming Vienna. The assassination of Franz Ferdinand by a Bosnian Serb linked to Serbian intelligence was the spark that Austria-Hungary used to settle accounts with Serbia—and that set the alliance system in deadly motion.

The July Crisis¶

The five weeks between the assassination (June 28) and the outbreak of general war (August 4) represent one of history’s most studied diplomatic failures:

Austria-Hungary, backed by Germany’s “blank check” of unconditional support (July 5-6), issued an ultimatum to Serbia on July 23 designed to be unacceptable. Serbia’s conciliatory response accepted most demands but not all. Austria-Hungary declared war on Serbia on July 28 and bombarded Belgrade the next day.

Russia ordered partial mobilization on July 29 to support Serbia, then full mobilization on July 30 as the military insisted partial mobilization was technically impossible. Germany demanded Russia halt mobilization (July 31), and when Russia refused, declared war on Russia (August 1) and France (August 3). Germany’s invasion of Belgium on August 4 brought Britain into the war.

The speed of the escalation astonished even those who caused it. Kaiser Wilhelm II, reading Serbia’s conciliatory reply, said: “This is more than one could have expected! A great moral victory for Vienna; but with it every reason for war disappears.” Yet by then, the military machinery was in motion, and the generals’ timetables overrode the diplomats’ second thoughts.

The War¶

The Western Front¶

The Schlieffen Plan nearly succeeded. German armies swept through Belgium and northern France, reaching within 30 kilometers of Paris by early September 1914. But the French counterattack at the First Battle of the Marne (September 5-12) halted the German advance. Both sides then attempted to outflank each other in the “Race to the Sea,” extending a line of trenches from the Swiss border to the English Channel.

For the next three and a half years, this line barely moved. The Western Front became synonymous with the futility of industrial warfare. Machine guns, barbed wire, and artillery created killing zones that no infantry assault could cross without catastrophic losses:

Verdun (February-December 1916): Germany’s attempt to “bleed France white” at the fortress city produced approximately 700,000 casualties (roughly evenly split) across ten months of fighting for negligible territorial gain.
The Somme (July-November 1916): Britain’s great offensive cost approximately 1.1 million casualties on both sides. On the first day alone—July 1, 1916—the British army suffered 57,470 casualties, including 19,240 dead, the worst single day in British military history.
Passchendaele (July-November 1917): British attacks through Belgian mud produced approximately 475,000 total casualties for an advance of eight kilometers.

New technologies—poison gas (first used by Germany at Ypres in April 1915), tanks (first deployed by Britain at the Somme in September 1916), and aircraft—proved unable to break the deadlock. Only the exhaustion of one side or the other, or the entry of fresh forces, could decide the outcome.

The Eastern Front and Other Theaters¶

The Eastern Front, though more mobile than the West, was equally devastating. Russia’s initial invasions of East Prussia and Austrian Galicia produced massive battles—Tannenberg (August 1914), where Germany destroyed an entire Russian army, and the Brusilov Offensive (June-September 1916), which broke the Austro-Hungarian army but cost Russia a million casualties.

The Ottoman Empire entered the war on Germany’s side in November 1914, opening fronts in the Caucasus, Mesopotamia, Palestine, and the Dardanelles. The Gallipoli Campaign (1915-1916)—an Anglo-French attempt to knock Turkey out of the war by seizing the Bosphorus—cost approximately 473,000 casualties and failed completely. The campaign’s architect, Winston Churchill, was forced from office; the defending commander, Mustafa Kemal, became Turkey’s national hero.

Italy entered the war against Austria-Hungary in 1915, fighting eleven battles on the Isonzo River for minimal gain. The Italian front tied down Austrian forces but produced no decisive result until the Central Powers’ collapse in 1918.

American Entry and the End¶

The United States entered the war on April 6, 1917, tipping the balance decisively. The immediate cause was Germany’s resumption of unrestricted submarine warfare, which threatened American shipping and commerce. The Zimmermann Telegram—a German proposal for a Mexican alliance against the United States—provided additional motivation.

American entry was transformative not because of immediate military impact—significant American forces did not reach France until 1918—but because of what it represented. The United States brought a population of 100 million, the world’s largest economy, and virtually unlimited industrial capacity. Germany, already blockaded and exhausted, now faced an adversary it could not outlast.

Germany’s Spring Offensive of 1918—a final gamble using troops transferred from the Eastern Front after Russia’s collapse—nearly broke through Allied lines. But the offensive exhausted Germany’s reserves, and the Allied counteroffensive from August 1918, spearheaded by fresh American divisions and British tanks, pushed the German army back inexorably. On November 11, 1918, Germany signed an armistice. The Kaiser had abdicated two days earlier; revolution swept through German cities; the empire was finished.

Consequences¶

The Destruction of Empires¶

The war destroyed four empires and remade the map of Europe and the Middle East:

The German Empire was replaced by the Weimar Republic, burdened by Versailles and internally fragile.
Austria-Hungary dissolved entirely into successor states: Austria, Hungary, Czechoslovakia, Yugoslavia, and parts of Poland, Romania, and Italy. The multinational empire that had governed Central Europe for centuries simply ceased to exist.
The Russian Empire collapsed into revolution. The Bolshevik seizure of power in November 1917 created the Soviet Union—the world’s first communist state, which would shape global politics for the rest of the century. Russia’s exit from the war through the Treaty of Brest-Litovsk (March 1918) cost it Finland, the Baltic states, Poland, Ukraine, and Belarus.
The Ottoman Empire was dismembered. The Sykes-Picot Agreement (1916) between Britain and France had secretly divided Ottoman territories in the Middle East. The postwar settlement created mandates—Iraq, Syria, Lebanon, Palestine, Transjordan—whose borders, drawn by European diplomats with little regard for local realities, remain the source of conflict a century later.

The Treaty of Versailles¶

The Paris Peace Conference of 1919 produced a settlement that satisfied almost no one:

Germany was forced to accept sole responsibility for the war (the “war guilt” clause), pay massive reparations, cede territory (Alsace-Lorraine to France, parts of Prussia to Poland, all colonies), limit its army to 100,000 men, and accept Allied occupation of the Rhineland. The terms were humiliating but not crippling—Germany remained Europe’s most populous and potentially most powerful state. The treaty created resentment without preventing recovery, the worst of both worlds.

The League of Nations, Woodrow Wilson’s great project, was established to prevent future wars through collective security. But the United States Senate refused to ratify the Treaty, leaving the League without its most powerful potential member. Without American participation or independent military force, the League could condemn aggression but not prevent it.

The principle of national self-determination was applied selectively. New states were created for Poles, Czechs, and South Slavs, but not for Germans in Austria or the Sudetenland, Hungarians in Romania and Slovakia, or the peoples of the colonial world. The inconsistency created grievances that Hitler would later exploit.

Seeds of the Next War¶

The war’s settlement contained the seeds of its own destruction. Germany’s resentment, the fragility of the successor states, the absence of American engagement, the rise of revolutionary ideologies (communism and fascism), and the economic dislocations that culminated in the Great Depression created conditions that made another conflict likely. Marshal Ferdinand Foch, the Allied supreme commander, assessed the Treaty of Versailles with prophetic accuracy: “This is not a peace. It is an armistice for twenty years.” World War II began almost exactly twenty years later.

The Birth of Modern Warfare¶

World War I transformed the nature of armed conflict. The technologies it introduced or refined—machine guns, aircraft, tanks, submarines, poison gas, radio communication, strategic bombing—remained central to warfare through the rest of the century. The concept of total war—the mobilization of entire societies and economies for military purposes, the deliberate targeting of civilian populations and economic infrastructure—became the norm rather than the exception.

The war also introduced mass propaganda as a tool of state policy, the draft as a permanent feature of modern states, and the idea that governments bore responsibility for the economic welfare of populations mobilized for war. The welfare state, in many respects, was born in the trenches.

The Transformation of the State System¶

Before 1914, five European powers—Britain, France, Germany, Austria-Hungary, and Russia—dominated global politics in a system of flexible balance of power diplomacy inherited from the Congress of Vienna. After 1918, two of those powers (Austria-Hungary and the Ottoman Empire) had ceased to exist, one (Russia) had undergone revolutionary transformation, one (Germany) was prostrate, and one (France) was exhausted. Britain remained standing but depleted. The United States, though retreating into isolationism, had demonstrated that European affairs could no longer be settled without reference to non-European powers.

The war thus began the shift from European to global politics—a shift completed by World War II and the rise of American and Soviet superpowers.

Sources & Further Reading¶

The Sleepwalkers: How Europe Went to War in 1914 by Christopher Clark — A masterful account of the July Crisis and its origins, arguing that the war resulted from shared responsibility rather than German aggression alone.
The Guns of August by Barbara W. Tuchman — The Pulitzer Prize-winning narrative of the war’s first month, demonstrating how military plans and political miscalculations turned a Balkan crisis into a world war.
The First World War by John Keegan — A comprehensive single-volume military history that combines strategic analysis with vivid depiction of the soldier’s experience across all fronts.
A Peace to End All Peace: The Fall of the Ottoman Empire and the Creation of the Modern Middle East by David Fromkin — Essential account of how wartime diplomacy—Sykes-Picot, the Balfour Declaration, the mandate system—created the modern Middle East and its enduring conflicts.
The Pity of War: Explaining World War I by Niall Ferguson — A provocative economic and counterfactual analysis challenging conventional explanations of why the war began, lasted so long, and ended as it did.