The casualties in the war are simply staggering...
And then they did it all again 20 years later.
Europe never recovered.
The world never recovered. 400 years of empire building, economic and political progress flushed down the toilet in twenty years. Followed by 45 years of communist infiltration, colonial wars and the whole Cold War.
And the burden fell mainly on us, and still falls on us as the Europeans are still incapable of pulling their weight. Only now our own fifth-column is on the verge of establishing a one-party woke corporate fascist state. All of which would not have happened except for WWI.
That war killed, on average, nearly 10,000 men a day, seven days a week, 52 weeks a year, for over four years.