By Jessica Lou
Germany, Austria-Hungary, and Italy created the Triple Alliance
Britain, France, and Russia created the Triple Entente
Heir to the Hungarian throne, Archduke Franz Ferdinand was assassinated by Serbian Gavrilo Princip, a part of the Black Hand.
A German submarine sank the British passenger ship Lusitania, leaving 1,198 people dead, 128 of them US citizens.
Trench warfare was created on the Western Front to protect from enemy fire.
Germany launched a massive attack against the French near Verdun. Each side lost more than 300 thousand men.
Germans announced their policy of unrestricted submarine warfare, where German submarines would sink without warning any ship in the waters around Britain.
Arthur Zimmermann, Germany's foreign secretary, sent a telegram to the German ambassador in Mexico. The message said Germany would help Mexico conquer the US land if they allied with them. This angered the US.
Civil unrest in Russia brought their czar government to a collapse.
President Wilson asked Congress to declare war. They entered the war on the side of the Allies.
President Wilson drew up a series of proposals, outlining a plan for achieving a just and lasting peace. It was called the Fourteen Points.
The Germans sent nearly all its forces to the Western front, but they lost against the Allies at the Marne River.
Germany and Russia signed the Treaty of Frest-Litovsk, ending the war between them.
The Germans signed an armistice, or an agreement to stop fighting. World War I came to an end.
The Treaty of Versailles between Germany and the Allied powers was signed.