Vietnam was more in the Soviet camp, whereas the Khmer Rouge was supported by China.
Even Ho Chi Minh remarked that he would rather smell French s___ for five years, than Chinese s___ for a thousand years.
And also in 1979, there was a brief border skirmish between Vietnam and China.
“Vietnam was more in the Soviet camp, whereas the Khmer Rouge was supported by China.”
Ho wanted to be friends with the US but he was a commie and we couldn’t have that.