World War I Summary

  • Last updated on November 10, 2022

World War I devastated the Great Powers of Europe and brought sweeping consequences for the entire world, including the slaughter of millions, the reshaping of empires and colonial territories, deadly innovations in warfare, and an unstable peace that eventually ushered in the even more destructive World War II.

Summary of Event

The advent of World War I came as a surprise to few astute observers, but the carnage it wrought, especially in the very heart of Europe, was a great shock to civilized nations. War fever had gripped much of Europe prior to the outbreak of World War I, most thinking that a quick war would settle the various balance-of-power considerations then motivating European governments. The two previous Balkan Wars of 1912 and 1913, Balkan Wars (1912-1913) although nasty, had been quite local affairs, so even after the assassination of the Austro-Hungarian Empire’s Archduke Francis Ferdinand by a disgruntled Bosnian Serb in Sarajevo, few believed that such an event would trigger the most devastating war waged in human history to date. With the benefit of hindsight, however, several factors can be seen as setting the stage both for the outbreak of the war and for its unprecedented destructive impact. World War I (1914-1918)[World War 01] [kw]World War I (June 28, 1914-Nov. 11, 1918) [kw]War I, World (June 28, 1914-Nov. 11, 1918) World War I (1914-1918)[World War 01] [g]East Asia;June 28, 1914-Nov. 11, 1918: World War I[03550] [g]Europe;June 28, 1914-Nov. 11, 1918: World War I[03550] [g]Japan;June 28, 1914-Nov. 11, 1918: World War I[03550] [g]Russia;June 28, 1914-Nov. 11, 1918: World War I[03550] [g]Soviet Union;June 28, 1914-Nov. 11, 1918: World War I[03550] [g]United States;June 28, 1914-Nov. 11, 1918: World War I[03550] [g]Worldwide;June 28, 1914-Nov. 11, 1918: World War I[03550] [c]Wars, uprisings, and civil unrest;June 28, 1914-Nov. 11, 1918: World War I[03550] [c]World War I;June 28, 1914-Nov. 11, 1918: World War I[03550] [c]Military history;June 28, 1914-Nov. 11, 1918: World War I[03550] Francis Ferdinand William II George V Wilson, Woodrow [p]Wilson, Woodrow;World War I[World War 01] Nicholas II

Background Factors

Among the major causes of World War I were the rising nationalist sentiments among governments and peoples throughout the world, especially in Europe. This involved not just the rise of nationalist sentiments in the Balkans as expressed in the royal assassination but also long-term rivalries among the major European powers. The French resented the loss of the Alsace-Lorraine to the Germans in the Franco-Prussian war of 1870-1871. Germany feared the rising tide of Slavic nationalism, especially in Russia, whose prestige in the Balkans had grown even as it began a rapid military buildup. In the weeks prior to the war, popular support for martial action in Germany, the Austro-Hungarian Empire, and France was palpable. Adding to this were the frustrated national aspirations of minority populations not only of Serbs but also of Poles, Ukrainians, and Ruthenians against German, Austrian, and Russian imperial domination.

Coupled with rising nationalism was a growing arms race, as the major powers—in particular Germany, France, Great Britain, the Austro-Hungarian Empire, and Russia—sought to expand their military capabilities, develop weaponry and naval capacities, conscript large armies, and perfect the process of rapid mobilization of forces. This expansion of power extended to the far-flung colonial holdings of Germany, Great Britain, and France, as well as to the control over neighboring minority populations exerted by Russia and the Austro-Hungarian Empire. Other smaller powers, including Turkey, the new Balkan states, Italy, and Spain also competed for territorial sway, while the United States and Japan, fresh from victories over Spain and Russia, respectively, also expanded their political and economic influence, especially in the Pacific region. The emphasis on naval power grew, as almost all of the major world powers raced to build battleships. Britain and Germany were foremost in this shipbuilding push, with the United States, France, Japan, and the Austro-Hungarian Empire following, and even Italy and Russia joined the race for dominance of the seas. World War I, then, would be fought not only in Europe but also on the high seas and in the colonial territories of the European powers.

Another major factor in the dynamic movement toward war was a complicated series of diplomatic treaties and defensive alliances meant to assure each major power of military support should war break out. Germany maintained an alliance guaranteeing support to the Austro-Hungarian Empire, even as Russia and France allied themselves against the threat of German aggression. Britain remained largely aloof from such alliances, preferring a policy of neutrality, but even it was party to an agreement guaranteeing Belgian neutrality, which would eventually be violated by Germany. The defense pacts implied, among other things, that any threat of aggression against an ally would initiate mobilization of forces by treaty partners, and, once initiated, these mobilizations would be difficult to reverse.

Still, the economic interdependence and trade among European countries was significant, and the blood ties between European monarchies suggested that the diplomatic and peaceful resolution of disputes could be achieved. George V of England, Emperor William II of Germany, and Czar Nicholas II of Russia were all related to one another and presumably had no intention of exposing their peoples to any prolonged or destructive war. Despite them, however, such a war began during the summer of 1914, as the Great Powers of Europe began to march inexorably toward what each thought would be a short and decisive confrontation but what instead descended into four years of brutal war.

Road to War

The road to war began with the assassination of Francis Ferdinand on June 28, 1914, by a young Serbian member of the ultranationalist Black Hand movement, which was not officially supported by Serbia. Austria accused the government of Serbia of having sponsored the assassination and, after three weeks of deliberation, demanded that Serbia make humiliating concessions or face war. Germany initially pushed Austria toward invasion of Serbia, but on actually seeing the conciliatory response of Serbia reconsidered. Serbia agreed to do everything Austria demanded, with the exception of permitting Austrians to participate in the judicial action against perpetrators found in Serbia. This, Serbia said, should be submitted to international arbitration. By this time, Austria was already engaged in a partial mobilization. Russia, despite threats from Germany, secretly agreed with Serbia that it would mobilize, and Serbia itself—not trusting to a peaceful Austrian response—also mobilized.

Austria rejected the conciliatory Serbian reply to its ultimatum, even as Britain proposed a peace conference, which was rejected by Germany. Austria bombarded Belgrade on July 29, and Russia ordered a general mobilization on the following day. Germany demanded that France declare that it would remain neutral in any war between Germany and Russia. The French responded that they would pursue their own best interest and then mobilized their troops. Germany responded on August 1 by declaring war on Russia and on August 3 by declaring war on France.





Britain, hoping to remain neutral, sought guarantees from both France and Germany for respect of British neutrality. France agreed, but Germany demurred from a clear response, and when German troops invaded neutral Belgium on August 4, Britain was compelled to declare war on Germany. The pattern of mutual defense alliances had drawn all of the major powers of Europe into war. Italy remained neutral. Japan declared war on Germany on August 23, while Turkey joined the Germans as part of the Central Alliance on November 3. Within four months, what began as a European war had already taken on a more global coloration, as Japan seized German island territories in the Pacific Ocean. Germany and Britain clashed in naval battles off the coast of Chile in the Pacific and off the Falkland Islands in the South Atlantic, as massive armies squared off against one another in Europe. Germany initially enjoyed a rapid forty-day advance deep into French territory, but the Battle of the Marne Marne, First Battle of the (1914) in September ended any German hopes for a swift victory.

A terrible war of attrition on the western front followed, as none of the combatants could score a decisive victory during four years of carnage. Serbia fended off Austria’s military offensive, even as Russia and the combined German and Austro-Hungarian forces largely fought to a standstill in a seesaw battle that saw Russia crush initial Austrian advances in Poland, followed by German reinforcement that led to a swift advance nearly to the gates of Moscow, before the Russians repelled the central power offensive. The war spread even to South Africa, as German and British forces clashed there. By the end of 1914, the hopes for swift victory were met by stalemate on every front, as casualties mounted to unprecedented levels. The one Great Power remaining out of the fray was the United States, which declared neutrality.

A War of Attrition and Frustration

New kinds of warfare and weapons were introduced as the war continued. Trench warfare on the western front saw the use of heavy artillery, machine guns, tanks, and even flamethrowers, all of which reaped a bitter harvest of casualties. On April 22, 1915, Germany introduced the use of chlorine gas at the Battle of Ypres. Ypres, Second Battle of (1915) This weapon, although deadly, was unpredictable and offered no real military advantage. Despite this, various deadly gases, including mustard gas, were later introduced.





At sea, Britain established its dominance with its victory in the naval battle of Jutland in late May, 1916. Although the British sustained heavier damage, Germany’s fleet was sufficiently reduced that it no longer played a decisive role in the war. However, Germany’s submarine forces continued to wreak havoc on Allied shipping in the Atlantic and began a policy of unrestricted submarine warfare against all shipping, including that of neutral parties in 1916. Submarines;World War I[World War 01] The sinking of the Lusitania Lusitania (ship) in May, 1915, served as a turning point in U.S. opinion against Germany, as more than one hundred American lives were lost. Still, the United States persisted in its policy of neutrality. Only after unrestricted German warfare did the United States break diplomatic relations with Germany in February, 1917, and deploy ground forces during the fall of that year.

The global nature of the conflict was underscored as Britain moved against Ottoman holdings in the Middle East. British forces advanced rapidly through southern Iraq in 1915, only to be stopped at Kut by Turkish forces, even as Ottoman forces unleashed a genocide against Armenians that eventually left as many as two million civilians dead. Trench warfare came to characterize Allied efforts to gain a foothold in Asia Minor against Turkey. Forces from Australia and New Zealand joined the British in the ill-fated Gallipoli Campaign Gallipoli Campaign (1915-1916) of that year. The Austro-Hungarian Empire, with help from Bulgaria, managed to subjugate Serbia in 1915. German forces in southwestern Africa were defeated by British-supported South African forces, and Anglo-French forces eventually defeated Germany in the Cameroons in February, 1916, but in Central and East Africa, German forces continued fighting until the war’s end in 1918. In the Middle East, Britain collaborated with Arab nationalists in 1917 to mount attacks against Ottoman holdings in Arabia and Palestine, consolidating advances made against Turkish forces in oil-rich Iraq.

The War Ends

Three decisive diplomatic events occurred in 1917 that eventually determined the outcome of World War I. First, in January the Allies promised independence to peoples living under Central Power rule. The Austro-Hungarian Empire immediately saw the implication of this for its multinational empire of Poles, Czechs, Slovenes, Croats, Serbs, and Rumanians, and began to seek a negotiated end to the war. Second, the Germans had encouraged and assisted the return of Vladimir Ilich Lenin to Russia, in hopes that a Bolshevik victory would lead to Russian withdrawal from the war. The Bolshevik October Revolution October Revolution (1917) realized this hope, allowing Germany to focus its military assets on the western front. However, the U.S. entry into the war on the side of the Allies, the third decisive event, more than compensated the Allies for the loss of Russia. The U.S. forces—deployed under the slogan of “making the world safe for democracy” and backed by the powerhouse American industrial economy—and their military weaponry began flooding into Europe. The Allies repulsed three major German offensives in 1918. Austria and Bulgaria fell to Allied forces, as Ottoman forces were routed. On the western front, the British, Canadians, Australians, Americans, and French pressured the German Hindenburg line, which they breached in September. Germany, bereft of allies and with a navy in mutiny, sued for peace. An armistice was signed on November 11, 1918.


Unprecedented in its bloodshed and destructiveness and in the lack of inhibitions restraining the use of new and more destructive weaponry and forms of warfare, World War I provoked a worldwide sense of revulsion at what supposedly civilized peoples were capable of doing to one another. The number of dead is estimated to have been about 8.5 million; 5 million among the Allies and 3.5 million among the Central Powers. That figure does not include civilian deaths or the even more significant numbers of dead produced by the Spanish flu epidemic that struck in 1917 or the Armenian genocide of 1915.

The war provoked the emergence of communism in Russia, which was quickly embroiled in a civil war of its own that produced around 3 million refugees. These refugees from the Russian Civil War were added to the 10 million people in Europe and the former Ottoman Empire who were displaced as a result of the world war. The suffering inflicted on civilian populations was unmeasurable. A whole generation was scarred by these human losses, especially in the countries most centrally involved, including France, Germany, Russia, and Britain, each of which lost around one million dead.

The rise of communism during World War I set the stage for a century of ideological conflict of global proportions. Conscious of new security threats, governments throughout the world introduced visa and passport requirements in an effort to protect and control their borders. Former territorial holdings and colonies of the Central Powers fell under new administrative authority, as the principle of self-determination gained currency and eventually led to a proliferation of newly independent states. The experience of war even in the colonies of Allied countries, such as British India, stoked the fire of independence movements that would eventually blossom after World War II.

World War I stimulated a proliferation in international cooperation and diplomacy, with the creation of the League of Nations League of Nations and numerous related international bodies, but national rivalries after the war prevented these new institutions from curbing the nationalist resentments that would eventually lead to the outbreak of World War II. Indeed, attempts to assign blame began immediately after World War I, with the French at the forefront of those seeking major punishment for Germany. Germans, on the other hand, felt both undefeated and improperly maligned. Despite efforts by Woodrow Wilson to moderate the terms of the peace, the Treaty of Versailles of 1919 Versailles, Treaty of (1919) placed blame for the war squarely on Germany, imposing territorial transfers and reparations on that nation. The territorial transfers precipitated major emigration out of former German territories. Although most of the reparations were never actually paid, many Germans deeply resented them, and this resentment reinforced German nationalism, which was further manipulated by Adolf Hitler and the Nazi Party in the 1930’s. Many historians regard World War I and its complicated conclusion as a major cause of World War II, which was even more global and more devastating than had been World War I—supposedly “the war to end all wars.” World War I (1914-1918)[World War 01]

Further Reading
  • citation-type="booksimple"

    xlink:type="simple">De Groot, Gerard J. The First World War. New York: Palgrave, 2001. A trim summary of the origins, major military campaigns, and life in the trenches and on the home fronts. A useful introduction for the beginning student.
  • citation-type="booksimple"

    xlink:type="simple">Fromkin, David. Europe’s Last Summer. New York: Alfred A. Knopf, 2004. A prominent historian revisits the old questions regarding both the causes and the responsibility for the outbreak of the war.
  • citation-type="booksimple"

    xlink:type="simple">Gilbert, Martin. First World War. New York: HarperCollins, 1995. With detailed year-by-year coverage, Gilbert provides colorful details about the events related to World War I.
  • citation-type="booksimple"

    xlink:type="simple">Mosier, John. The Myth of the Great War: A New Military History of World War I. New York: HarperCollins, 2001. This military history offers new assessments of the military aspects of World War I, and of the decisiveness of American economic and military contributions to Allied victory.
  • citation-type="booksimple"

    xlink:type="simple">Winter, Jay and Blaine Badgett. The Great War: And the Shaping of the Twentieth Century. New York: Penguin Books, 1996. A pictorial history of World War I and its aftermath offering both a visual record and an analytic assessment of key personalities, events, and, trends.

Outbreak of World War I

Germany Begins Extensive Submarine Warfare

Spain Declares Neutrality in World War I

Germany Launches the First Zeppelin Bombing Raids

Germany Uses Poison Gas Against Allied Troops

Fokker Aircraft Are Equipped with Machine Guns

German Torpedoes Sink the Lusitania

Poppies Become a Symbol for Fallen Soldiers

United States Enters World War I

France Executes Mata Hari

Harding Eulogizes the Unknown Soldier

All Quiet on the Western Front Stresses the Futility of War

Categories: History