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Archduke Franz Ferdinand is assassinated in Sarajevo. His death starts WWI.
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Russia mobilizes its vast army to intervene against Austria-Hungary in favor of its ally, Serbia. This creates a domino effect that leads to the assemblage of the rest of the European Great Powers, and inevitably to the outbreak of hostilities.
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Germany invades Belgium.
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The Germans fired shells filled with chlorine gas at Allied lines. The result is the near-collapse of the French lines.
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A German submarine sinks the passenger liner Lusitania. The ship was carring 1,198 people, 128 of them American.
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Kaiser Wilhelm suspends unrestricted submarine warfare as a reation to international outrage at the sinking of the Lusitania and other neutral passenger lines. It is an attempt to keep the US out of the war, but it extremely obstructs German efforts to prevent American supplies from reaching France and Britain.
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Britain employs the first tank ever used in battle at Delville Wood. They failed to be the decisive weapon, but were good for breaking through barbed wire and clearing a path for the infantry.
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Germany restarts unregulated submarine warfare in European waterways. This action draws draws the US into the war and causes of eventual defeat of Germany.
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The Zimmermann Telegram was a message from German foreign secretary Arthur Zimmermann proposing that Mexico side with Germany in case of war between Germany and the US. In exchange, Germany promises to return to Mexico the "lost provinces" of Texas and much of the rest of the American Southwest. Mexico turned down the offer, but the blowup at this interference pushes American public opinion to support entering the war.
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President Woodrow Wilson drafts his case for war to Congress.
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Congress authorizes a declaration of war against Germany. The US enters WWI on the side of France and Britain.
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Congress passes this act to authorize Wilson's draft. Wilson claims he sees no other option other than entering the war and signs the bill into law.
