Home > Conflict Casualties > World War I

World War I

Map or Europe

On 28 June 1914, in Sarajevo, a Serb nationalist assassinated Archduke Franz Ferdinand, heir to the Austro-Hungarian throne. Due to a network of competing alliances, a European history of nationalistic rivalry over colonies and military dominance, and the importance of being the first to mobilize reserve forces for war, this small event initiated what was then the largest conflict the world had ever experienced. The Austro-Hungarians, allied with Germany, made demands on Serbia, backed by Russia, which was in turn allied with France. Great Britain supported Russia and France in what was known as the Triple Entente. In the event of war with Russia and France, the German Schlieffen Plan envisioned a quick victory over France, which necessitated violation of the neutrality of Belgium, so that it could then turn all its attention to Russia, which would mobilize much more slowly. Within one week of Austro-Hungary's 28 July declaration of war on Serbia, most of Europe was embroiled. Japan, an ally of Great Britain, joined in on 23 August, thus extending the conflict to the Pacific. The Ottoman Empire also would come in on the side of Germany and extend the war into the Middle East, while Italy would side with Triple Entente in 1915. By the time the Great War (as it was known prior to World War II) ended in 1918, more than nine million soldiers and a further five million civilians had died.

The initial German advance through Belgium and into France was successful, but ultimately ran out of steam short of Paris in the face of stiffening French and British resistance. As each side tried to outflank the other, a series of opposing defensive trenches soon stretched from the English Channel to Switzerland. Coupled with machine guns, barbed wire, and modern artillery, the fortified lines led to a static battle of attrition on this front. The introduction of chemical weapons and the tank brought short-term advantages but no significant change in the front lines. The battle lines were not as static in the East, but neither side could gain the upper hand over the other.

The year 1917 saw great changes in the war. Cumulative French manpower losses and mutinies brought its military to the brink of collapse. Similar war weariness contributed to Czar Nicolas' abdication and Russian withdrawal from the conflict. But the German use of unrestricted submarine warfare, which resulted in the death of U.S. citizens on the high seas, brought the United States into the war on 6 April. The subsequent injection of the American Expeditionary force and its two million soldiers offset Germany's ability to focus all its forces on the western front in 1918. A series of German offensives in early 1918 brought the first major gains of territory in the west since 1914, but Allied ripostes regained much of the ground and drove Germany back toward its own borders as the year progressed. By October, the Austro-Hungarian Empire had disintegrated and the Ottoman Empire had surrendered. On 11 November 1918, Germany agreed to a ceasefire. With the signing of the Treaty of Versailles on 28 June 1919 the "war to end all wars" formally ended.