World War 1, lasted from 1914 to 1918. World War 1 began as a local European conflict between Austria-Hungary and Serbia on July 28, 1914
It was transformed into a general European war by the declaration of war made by Germany against Russia, on August 1, 1914.
These intermingled conflicts eventually became a global war involving thirty two nations, twenty eight of which, known as the Allies and the Associated Powers, and including Great Britain, France, Russia, Italy and the United States, opposed the coalition known as the Central Powers, consisting of Germany, Austria-Hungary, Turkey and Bulgaria.
The immediate cause of the war between Austria-Hungary and Serbia was the assassination on June 28, 1914, at Sarajevo, capital of the Austro-Hungarian province of Bosnia, of the Archduke Francis Ferdinand, heir-presumptive to the throne of Austria-Hungary, by Gavrilo Princip, a serb nationalist.
The fundamental causes of the conflict, however, were rooted deeply in the European history of the previous century, particularly in the political and economic policies of the nations of Europe after the year 1871, which marked the emergence of Germany as a great world power.
The unarmed British passenger ship Lusitania was torpedoed and sunk by a German submarine on May 7, 1915. This outraged the American public opinion against Germany.
Hostillities between the Allied and Central Powers continued until the signing of the Armistice on November 11, 1918, a period of four years, three months and fourteen days. The aggregate direct war costs of all the belligerents amounted to about 186 billion dollars.
Casualties in the land forces amounted to over 37 million; in addition deaths amoung civilian populations caused indirectly by war approximated 10 million.