Key Terms & Events of World War I

Chemical weapons were first systematically used in World War I, primarily as a strategic measure to intimidate, disorient, and injure soldiers occupying defensive positions in trenches. Such weapons were first employed by the German Army at the Battle of Ypres in April 1915 and then by the British Army in September 1915 at the Battle of Loos. The types of weapons employed ranged from disabling chemicals, like tear gas and mustard gas, to more deadly substances, particularly chlorine. While only three percent of combat deaths (less than 90,000 men) were caused by gas, hundreds of thousands of soldiers were permanently injured by gas attacks. Yet as the use of chemicals became more common both sides developed new countermeasures, including gas masks, which limited its overall usefulness in battle. The widespread use of these agents of chemical warfare, as well as advances in their delivery and effectiveness, led to World War I being known as "the chemists' war". 

The Hindenburg Line was a German defensive position built on the Western Front along the Aisne River. With fewer soldiers than their opponents, an army divided between two fronts, and lagging munitions production on the home front, the German offensive at the Battle of Verdun on the Western Front had been a costly failure and Anglo-French attacks continued to inflict serious losses on the German army at the Somme. Realizing the likely need to withdraw back to intensively fortified defensive positions in order to hold out against the more numerous British and French forces, construction of the Hindenburg Line began in September 1916. The defenses were built by German companies using early mass production techniques, while a mix of German workers, Belgian forced laborers, and Russian prisoners of war dug the trenches. The line stretched 90 miles long and was built for a garrison of 20 divisions (about 300,000 men), one every 4.5 miles. The Line also integrated important infrastructure, including buried telephone cables and light railways to carry supplies. Fields of barbed-wire up to 100 yards deep were also placed in front of the trench system. The Hindenburg Line was attacked several times in 1917 and 1918 and was finally broken in September 1918, during the Hundred Days Offensive. 

Total war is a type of warfare that mobilizes domestic society and all of its resources in the war effort, and prioritizes warfare over civilian or domestic matters. It also does not prohibit attacks on the civilian space, infrastructure, and supplies that support the enemy war effort. Thus, in total war the division between combatants and non-combatants diminishes or even vanishes as opposing sides consider every human resource as contributing to the war effort. The unprecedented level of violence, powered by new machines and technologies that originated in the second industrial revolution, also characterizes World War I as a total war. Widespread use of chemical warfare and new high-volume weapons - both products of industrialization - significantly increased casualties using fewer resources. Even more than simply the means of warfare, the extent to which such tactics were used indicate a total war strategy during World War I. Such technologically-advanced and lethal modes of violence were often brought to civilian spaces, as evidenced by the use of zeppelins for bombing raids in England. In this way, the rules of war and limits of violence that were generally observed during European wars throughout the nineteenth century gradually eroded or were even completely disregarded. 

Following the end of hostilities with the armistice on November 11, 1918, the Paris Peace Conference convened in January 1919 at Versailles, just outside of the city, to establish the terms of a peace treaty between the thirty nations invited to participate in deliberations. Dominating the negotiations at the conference were the representatives of the United Kingdom, France, the United States, and Italy, who became known as the “Big Four.” The result of months of discussions, the Treaty of Versailles articulated the many compromises reached at the conference, including the formation of the League of Nations (a precursor to the United Nations), the partitioning (or redistributing) of the former Ottoman Empire and other territories between Britain and France, the restricting of the German army, and the seizure of German territory and natural resources along the Rhine River. Perhaps the most debated section of the treaty, the “War Guilt” clause charged Germany with responsibility for the war and made them liable to pay financial reparations to the Allies totaling 32 billion U.S. dollars. Many historians claim that the combination of a harsh initial treaty and the subsequent lax enforcement of its provisions fostered deep German resentment of its creators and paved the way for the upsurge of German militarism in the 1930s, ultimately leading to World War II. 

Trench Warfare is a battle tactic in which opposing forces attack and defend from relatively permanent systems of narrow excavations dug into the ground, usually resorted to when the superior firepower of the defense compels the opposing forces to “dig in” so extensively as to sacrifice their mobility in order to gain protection. Trench warfare was a key aspect of fighting on the Western Front when armies faced each other in a line of trenches extending from the Belgian coast through northeastern France down to Switzerland. These trenches arose within the first few months of the war’s outbreak after German and French infantry offensives were made ineffective against the technological improvements of the twentieth century, like the machine gun and rapid-firing artillery. The typical trench system in World War I consisted of multiple trench lines running parallel to each other and connected to each other and to the rear by perpendicular trenches, allowing for the movement of food, ammunition, troops, mail, and commands. Strategically, trench warfare provided relative protection until forces came “over the top” (engaged in offensives) to break through the enemy’s trench system by mounting infantry assaults preceded by intense artillery bombardments of the defending trenches. 

The Triple Entente (from French entente, "friendship or agreement") were a series of diplomatic treaties linking the Russian Empire, France, and Britain through the Franco-Russian Alliance of 1894, the 1904 Entente Cordiale between Britain and France, and the Anglo-Russian Convention of 1907. The series of alliances between the three nations was a key diplomatic and military counterweight to the Triple Alliance of Germany, Austria-Hungary, and Italy (Italy ultimately did not side with Germany and Austria during World War I, but maintained neutrality until joining the Entente Powers after signing the Treaty of London in 1915). Yet many historians have contended that such an alliance system played a significant part in the days that World War I grew from a localized conflict in the Balkans to a global war. The alliance of Russia with Europe's two most prominent democracies was also not without controversy. Many Russian politicians distrusted the liberal French Republic and recalled British diplomatic competition in the Ottoman Empire following the Crimean War in the 1850s. In turn, French and British journalists, academics, and diplomats found the reactionary tsarist regime troubling. 

On April 6, 1917, the United States entered World War I. Over the next eight months, President Woodrow Wilson outlined his vision of an end to the war that would bring about a “just and secure peace." On January 8, 1918, Wilson presented fourteen principles for world peace to a joint session of Congress. The majority of the fourteen points addressed specific territorial issues among the combatant nations. Five concerned general principles for a peaceful world, including open covenants (treaties or agreements), freedom of the seas, free trade, reduction of armaments, and the right to self-determination by all people. The fourteenth point proposed what would be the League of Nations, an independent, multi-national body to guarantee the “political independence and territorial integrity [of] great and small states alike.” The address was celebrated in the United States and across the world as a landmark of progressive international relations. Wilson relied on the Fourteen Points as the basis for negotiating the Treaty of Versailles after the end of the war. Yet the Treaty did not fully realize Wilson’s vision and many, including Wilson himself, were left disillusioned by the end of the treaty negotiations.