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The murder of the heir to the Austro-Hungarian throne by a Bosnian Serb nationalist triggered a month-long series of ultimatums and diplomatic crises that activated a complex web of military alliances across Europe, leading to a global conflict that reshaped the world. -
The U.S. maintained a policy of neutrality during the early years of World War I, proclaimed by President Woodrow Wilson in 1914. However, this neutrality was eroded by Germany's unrestricted submarine warfare, which led to the sinking of the Lusitania and other American ships -
It halted Germany's rapid advance into France, saving Paris and forcing the war onto the Western Front to become a brutal, prolonged conflict of trench warfare instead of a quick, decisive German victory. -
It significantly increased anti-German sentiment in the United States and pressured the U.S. to abandon its neutrality. -
It was a symbol of French resistance and a brutal, costly battle of attrition that significantly weakened the German army and contributed to their eventual defeat in World War I. -
It led the U.S. to threaten to break diplomatic ties with Germany, prompting Germany's "Sussex pledge" to restrict submarine warfare -
It inflicted heavy casualties on the German army, forcing a strategic retreat, and provided the British military with crucial experience that led to improved tactics and eventual victory in later years. -
A secret communication from Germany to Mexico that proposed a military alliance against the United States during World War I, and its interception and publication inflamed American public opinion, directly leading to the U.S. declaring war on Germany. -
A World War I naval tactic to sink any ship, including passenger vessels, in the waters around Britain to disrupt supply lines and starve Britain into submission. -
It was a decisive turning point that tipped the scales in favor of the Allies, ultimately leading to Germany's defeat and an Allied victory. -
A U.S. law that establishes the authority to draft citizens into the armed forces, creating the Selective Service System. -
It protects national security by criminalizing the unauthorized disclosure of sensitive government information. -
Provided critical manpower, morale, and resources to exhausted Allied armies in France. -
They offered a vision for a just and lasting peace after World War I, addressing the war's causes, and introduced revolutionary concepts like national self-determination and collective security through the League of Nations. -
It killed an estimated 50 to 100 million people worldwide, more than World War I, and infected one-third of the global population. -
It allowed Germany to focus on the Western Front, temporarily shifting the war's momentum. -
It represented a major challenge to freedom of speech and the press, leading to a pivotal debate over states' rights versus federal power. -
It was the largest and deadliest battle in U.S. military history, and a crucial part of the final Allied offensive that broke the German army and ended World War I. -
Commemorating the end of a devastating conflict and honoring the sacrifices of those who served. The day is a solemn observance of remembrance, often including a moment of silence and the laying of wreaths. -
They ended World War I, established the League of Nations for collective security, redrew the map of Europe, and imposed harsh terms on Germany that caused deep resentment, ultimately sowing seeds for future conflict, including World War II.