Title: World War I | History, Summary, Causes, Combatants, Casualties, Map, & Facts | Britannica
Headings: 
World War I
Top Questions
What was the main cause of World War I?
What countries fought in World War I?
Who won World War I?
How many people died during World War I?
What was the significance of World War I?
Explore the roles of Marie Curie, Mabel St. Clair Stobart, and Aileen Cole Stewart in World War I
The outbreak of war
Witness the beginning of World War I with the assassination of Archduke Franz Ferdinand on June 28, 1914

Content: How many people died during World War I? Some 8,500,000 soldiers died as a result of wounds or disease during World War I. Perhaps as many as 13,000,000 civilians also died. This immensely large number of deaths dwarfed that of any previous war, largely because of the new technologies and styles of warfare used in World War I.
Read more below: The last offensives and the Allies’ victory: Killed, wounded, and missing
Read more below: The outbreak of war: Technology of war in 1914
Trench warfare
Read more about trench warfare. What was the significance of World War I? Four imperial dynasties—the Habsburgs of Austria-Hungary, the Hohenzollerns of Germany, the sultanate of the Ottoman Empire, and the Romanovs of Russia—collapsed as a direct result of the war, and the map of Europe was changed forever. The United States emerged as a world power, and new technology made warfare deadlier than ever before.