Keep pulling the thread on Adolf Hitler.
On June 28, 1914, Archduke Franz Ferdinand, the heir to the Austrian throne, was assassinated by Serbian nationalist Gavrilo Princip.
Prior to World War I, Russia had promised protection to Serbia.
Following the assassination of Archduke Franz Ferdinand, Austria invaded Serbia, triggering a series of alliances that led to World War I.
Germany allied with Austria at the start of World War I, while France had a mutual defense alliance with Russia.
Germany invaded Belgium as a route to attack France, which triggered Great Britain's entry into World War I due to its alliance with Belgium.
In April 1917, the United States entered World War I, reinforcing British and French troops.
Russia's revolution during World War I allowed Germany to move soldiers from the Eastern Front to the Western Front.
A naval blockade by Allied forces was a key factor that forced Germany into submission in World War I.
On November 9, 1918, Kaiser Wilhelm abdicated his throne, ending the German Empire (Deutsche Reich).
On November 11, 1918, Germany's new social democratic government signed an armistice agreement with the Allies, ending World War I.
The Versailles Treaty imposed harsh conditions on Germany after World War I, including large financial reparations, loss of territory, and severe restrictions on its military.
The French army occupied the Ruhr Valley, Germany's primary industrial region, to seize industrial output as repayment for Germany's defaulted reparation payments.