Archduke Franz Ferdinand was assassinated by a Serbian nationalist terrorist group. This was the catalyst for WW1.

Austria-Hungary declares war on Serbia, officially starting WW1.

Germany crosses through Belgium on the path to France causing Britain to declare war on Germany due to the alliance between Britain and Belgium

The first battle of Marne was the first battle to introduce trench warfare.

The Lusitania was a British boat that had 128 American citizens on board that were all killed by a Nazi U-boat attack

The battle of Gallipoli is commonly regarded as one of the most intense battles of all time for its intensity

America intercepts a telegram sent from Germany to Mexico asking to aid Germany in declaring war on America

The Russian Revolution abolished the monarchy and established a socialist form of government.

The Congress agreed to declare war on Germany after the events of the Zimmerman note

The Treaty of Versailles marked the official end of WW1 with a treaty between countries.