World War One officially began in 1914 after an event that took place in the capital of Bosnia. On June 28, 1914, the Archduke Franz Ferdinand of Austria was assassinated by a terrorist group known as the Black Hand. The Archduke was the heir to the throne, so as imagined this caused much controversy which culminated into World War One.
|Archduke Ferdinand of Austria-Hungary was assassinated.|
In general, World War One was rooted into four general causes: Growing militarism, formation of defense alliances, nationalism, and colonial disputes. These four things increased tension between the countries and their leaders so much that any small event could have triggered an explosion. Indeed, the growing militarism made the countries paranoid; the defense alliances tied all the countries together so that a spark in one place inevitably involved everyone else; the nationalism warmed up the war engine faster through the support from the common man; the colonial disputes revealed that war was becoming inevitable and caused worry in the countries.
Eventually, countries had taken sides via the defense alliances. Another major event that brought the countries closer to war was another war: The Balkan Wars. This war was mostly between the countries in the Balkan peninsula, yet whenever Serbia rose to power, the Austrians felt threatened by its emergence. The two countries from there became rivals.
Therefore, whenever Ferdinand was assassinated, the Austrians demanded an apology from Serbia since they felt the Serbians were conspiring against the Austrians. When this occurred, a conflict happened and the two countries set up their armies. Due to the defense alliances and readiness by the people for war (via nationalism), the other countries became involved beginning with Russia supporting Serbia (Slavic nations), then Germany supporting Austria-Hungary (Germanic nations), and France supporting Russia. The whole continent became engulfed with war, and when Germany violated Belgian neutrality, the British joined in.
The United States wouldn't join the war until the last year of the war in 1917. Over time, due to Germany's unrestricted U-boat1 mobilization, they struck down all sorts of ships including ones with American people on them. Due to Germany therefore violating the Sussex Pledge and issuing the Zimmerman Note to Mexico, the United States declared war on Germany.
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