At one point, he was in jail for resisting the Americans. His father visited him, and asked "What the heck are you doing?" He answered "Fighting against the oppressor Americans!" His father responded "It's true that they're oppressors, but the communists are worse."
He didn't believe his father. When the Americans left, there was a victory parade through Hanoi. Which was composed only of communist regiments. He asked the other people involved in the resistance "Where are all the non-communist regiments, which were the majority of the fighters?" The answer was "On exercises in the country."
It turned out that the communists had infiltrated all of the non-communist resistance groups (of which there were many), and taken them over from the inside.
A few years later, with his life in danger from the communists, he fled Vietnam, became one of the boat people, and immigrated to America.