Triple Alliance It was a secret agreement between Germany, Austria-Hungary, and Italy. It was formed on 20 May 1882 and renewed periodically until it expired in 1915 during World War I.
Tiple Entente Refers to the understanding linking the Russian Empire, the French Third Republic, and United Kingdom of Great Britain and Ireland after the signing of the Anglo-Russian Entente on 31 August 1907.
Assassination of Archduke Franz Ferdinand 28 June 1914 in Sarajevo when they were mortally wounded by Gavrilo Princip.
THE U.S. DECLARES THE WAR
Zimmerman Note A secret diplomatic communication issued from the German Foreign Office in January 1917 that proposed a military alliance between Germany and Mexico. In the event that the United States entered World War I against Germany, Mexico would recover Texas, Arizona and New Mexico.
The sinking of Lusitania The sinking of the Cunard ocean liner RMS Lusitania occurred on Friday, 7 May 1915 during the First World War, as Germany waged submarine warfare against the United Kingdom which had implemented a naval blockade of Germany. The ship was identified and torpedoed by the German U-boat U-20 and sank in 18 minutes.
U.S. Declaration of War The 1917 United States declaration of war on Austria-Hungary, officially House Joint Resolution 169, was a resolution adopted by theUnited States Congress declaring that a state of war existed between the United States of America and the Austro-Hungarian Empire.