Why did Archduke Franz Ferdinand's assassination trigger World War 1?

Answer 1

Franz Ferdinand was the heir to the throne of the Austro-Hungarian Empire. He was murdered by Bosnian separatists with help from Serbian militants. Austria-Hungary blamed Serbia for helping the assassins, and after some failed negotiations, they declared war on Serbia.

Austria-Hungary's declaration of war triggered the complex system of alliances, which finally caused World War I.

1. Russia, who considered Serbia a close friend, began mobilizing their army against Austria-Hungary.
2. Germany, who was allied with Austria-Hungary, declared war on Russia.
3. Knowing that Russia and France were allies, Germany also declared war on France and launched an invasion of France through Luxembourg, Belgium and the Netherlands.
4. Britain demanded that Germany leave Belgium. When Germany ignored this, Britain declared war on Germany.
5. Knowing that the Ottoman Empire disliked Russia, Germany gave the Ottomans some warships, which the Ottomans used to attack Russia, thereby declaring war on them.

Other countries later joined the war (notably Italy and the United States), but this was the point where major fighting had started.