The most likely development in the 20th century that most directly weakened the European colonial states was the Second World War.
What did the Second World War do to colonial states?
Colonial states such as Britain and France suffered heavy economic and military damage during WWII which left them weakened.
As a result of this weakness, they were forced to allow a lot of their colonial dominions to gain independence.
Find out more on WWII at https://brainly.com/question/651584.
