Weak military, they weren’t able to fight of invaders like the barbarians.
Which philosophy focuses on internal happiness and harmony with nature?
Buddhism
Hồ Chí Minh led the Việt Minh independence movement from 1941 onward, establishing the Communist-ruled Democratic Republic of Vietnam in 1945 and defeating the French Union in 1954 at the Battle of Điện Biên Phủ, ending the First Indochina War.