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The assassination of Archduke Franz Ferdinand was the direct trigger for World War I, as it provided Austria-Hungary the pretext to declare war on Serbia. -
The United States adopted a policy of neutrality in World War I, officially declared by President Woodrow Wilson in August 1914, to avoid entanglement in what many Americans saw as a European conflict. -
It halted the German advance on Paris in 1914, preventing a quick German victory and leading to the stalemate of trench warfare that defined the rest of World War I. -
The attack by a German submarine killed 128 Americans, dramatically shifting U.S. public opinion against Germany and increasing pressure on the government to enter World War I. -
A symbol of French determination, its role in shaping military tactics toward attrition, and the huge human cost that made it one of the longest and bloodiest battles of the war. -
It prompted the German government to issue the "Sussex Pledge," which temporarily ended unrestricted submarine warfare and kept the United States out of World War I in 1916 -
It resulted in one of the largest and bloodiest battles in history, which led to significant changes in military strategy and had a profound impact on British society. -
It was a secret communication from Germany to Mexico in 1917, proposing a military alliance against the United States during World War I. -
It was a desperate German strategy in WWI to cripple Britain's supply lines, which initially put pressure on the Allies. -
It was a decisive turning point that ensured an Allied victory, marked a major shift in U.S. foreign policy from isolationism to global engagement, and established the U.S. as a major player in international affairs. -
Its role in authorizing conscription, which is the drafting of citizens into military service, and in managing a system for this purpose. -
Protecting national security by criminalizing the unauthorized disclosure of sensitive information and safeguarding government operations. -
It provided fresh troops and critical resources to the Allies in WWI, helping to tip the balance against the exhausted Central Powers and secure an Allied victory. -
Established President Wilson's vision for ending World War I, providing a basis for the Treaty of Versailles and shaping future international relations. -
Catastrophic global impact, its role in revolutionizing public health, and the lasting lessons it provided for future pandemics. -
Russia's exit from World War I, sealed by the Treaty of Brest-Litovsk in March 1918, was important because it allowed Germany to shift troops to the Western Front, temporarily strengthening the Central Powers. -
Controversial role in testing and solidifying the First Amendment's protection of free speech and press. -
It was the final Allied offensive of World War I, involved over a million American soldiers, and its success led to the German army's collapse and the eventual armistice on November 11, 1918. -
Marking the cessation of hostilities and leading to the eventual peace treaty. -
Officially ending World War I, reshaping the map of Europe, and establishing the League of Nations.