What started the First World War? Be consise but don't leave out important details

The First World War, also known as the Great War, began on July 28, 1914, and lasted until November 11, 1918. The immediate cause of the war was the assassination of Archduke Franz Ferdinand of Austria-Hungary by a Serbian nationalist in Sarajevo on June 28, 1914. However, the war was the result of a complex web of alliances, rivalries, and tensions between European powers that had been growing for decades.

1. Assassination of Archduke Franz Ferdinand: The Archduke of Austria-Hungary, Franz Ferdinand, and his wife were assassinated by Gavrilo Princip, a member of the Serbian nationalist group known as the Black Hand. Austria-Hungary blamed Serbia for the assassination.

2. Austria-Hungary's Ultimatum to Serbia: In response to the assassination, Austria-Hungary issued an ultimatum to Serbia, which Serbia partially rejected. Austria-Hungary then declared war on Serbia on July 28, 1914.

3. Activation of Alliances: The system of alliances that had been formed among the European powers over the previous decades came into play. Russia, bound by a treaty to Serbia, announced mobilization of its vast army in Serbia's defense. Germany, allied to Austria-Hungary by treaty, viewed the Russian mobilization as an act of war against Austria-Hungary, and after scant warning declared war on Russia on August 1.

4. Spread of the War: France, bound by an alliance with Russia, found itself at war against Germany and, by extension, on Austria-Hungary following a German declaration of war on August 3. Germany then invaded neutral Belgium, so as to reach Paris by the shortest possible route. This led Britain to declare war on Germany on August 4, in response to Germany's violation of Belgium's neutrality, which Britain had guaranteed by treaty.

5. Global Involvement: Over the next few weeks, these major powers brought their allies into the conflict, leading to the spread of the war across Europe and eventually into several other parts of the world.

In summary, the assassination of Archduke Franz Ferdinand was the spark that ignited the war, but the underlying causes lay in the complex web of alliances, militarism, imperialism, and nationalism that had been developing in Europe for decades.