War erupts in Europe one month following the assassination of Archduke Franz Ferdinand of Austria on June 28, 1914.
A new weapon is introduced during World War I as deadly poison gas is employed on the battlefields of Europe.
The Battle of the Somme begins in July 1916 and eventually becomes one of the bloodiest events in human history.
U.S. President Woodrow Wilson asks Congress for a declaration of war in April 1917 after Germany begins sinking American ships in the North Atlantic.
