World War One (1914-1918)
World War I is also known as the First World War, the Great War and the War To End All Wars.
It was a global military war which took place primarily in Europe from 1914 to 1918. Over 40 million casualties resulted, including approximately 20 million military and civilian deaths.
The immediate cause of the war was the assassination of Archduke Franz Ferdinand (June 28, 1914), heir to the Austro-Hungarian throne, by Serbian nationals. The retaliation by Austria-Hungary against Serbia activated a series of alliances that set off a chain reaction of war declarations. Within a month, much of Europe was in a state of open warfare.