Caused more than 16 million deaths (Civilian and Military)
Changed the nature of warfare
Advanced technology, medicine, weapons and mass production techniques
Shaped the first feminist movement
Drastically changed the social structure and landscape of Europe
Caused an economic depression in three countries
Caused the downfall of four monarchies (Russia, Germany, Ottoman and Austria-Hungary), creating many new countries in Europe
Only the USA profited from WWI, having sold arms to both sides, and joining the war quite late. They become a global power and held it for much of the 20th and 21st centuries.
The real question is...
Who is responsible for all of the above?
Germany hadn’t started the war. That blame lay on the Serbs, and the now-dissolved Austro-Hungarian and Russian Empires.
Surely, Germany was just guilty of honouring their alliances. So why do they take the blame?
Invading neutral Belgium violated an 80-year-old neutrality agreement.
The physical damage inflicted on Belgium, France and their people was horrific.
30,000+ civilians died and 120,000+ were enslaved to build railways and fortifications.
400,000 French civilians died, in addition to the 1.3 million French and colonial troops.
Germany used a "Scorched Earth Policy" whenever they were forced to retreat, destroying industry, infrastructure, agriculture and anything useful to their enemies.
These ideas aren't new to war, and almost every nation has similar atrocities. So why then?
Germany crossed paths with the oldest empires (Britain, France and Russia). Britain wished to make an example out of Germany, and France wanted revenge.