Four empires collapsed after WWI: Ottoman, Austro-Hungarian, German, and Russian.
The Aftermath of World War I saw drastic political, cultural, economic, and social change across Eurasia (Europe and Asia), Africa, and even in areas outside those that were directly involved.
Four empires collapsed due to the war, old countries were abolished, new ones were formed, boundaries were redrawn, international organizations were established, and many new and old ideologies took a firm hold in people's minds.
World War I also had the effect of bringing political transformation to most of the principal parties involved in the conflict, transforming them into electoral democracies by bringing near-universal suffrage for the first time in history, as in Germany (1919 German federal election), Great Britain (1918 United Kingdom general election), and Turkey (1923 Turkish general election).
World War I is one of the deadliest conflicts in history, with an estimated nine million combatants and seven million civilian deaths as a direct result of the war.
Most historians agree that American involvement in WW1 was inevitable by early 1917, but the march to war was accelerated by a letter penned by German foreign secretary Arthur Zimmermann.
During WW1, the U.S. Government tried to rename hamburgers as "liberty sandwiches" to promote patriotism.
The Schlieffen Plan, devised a decade before the start of WW1, outlined a strategy for Germany to avoid fighting at its eastern and western fronts simultaneously.