Sir, the Vietnamese Communists (when they were still North Vietnam) relied heavily on aid from the Chinese during the war. In return, then-PM Pham Van Dong recognized Chinese territorial sovereignty over the islands in the South China Sea (the Vietnamese call it the East Sea, but that’s another issue for another day). Of course, Pham’s recognition should have no legal effect, but that’s how desperate they were to defeat their Vietnamese brothers to the south.
The 1979 war was almost 40 years ago. They patched up rather quickly, with the state press organ, Nhan Dan, stating the government’s intention in the early 1980s to mend relations with their elder communist brothers to the north. The People’s Army of Viet Nam, and the secret police, General Department No. 2 and others, receive training and intelligence from Chinese and share tactics on keeping power. People wanted to hold memorials of that war in 2014 but were suppressed by the government. The Chinese are heavily invested in Vietnamese mining and manufacturing, so there is even less reason for the government to want to take the fight to China.
China has helped to kill or hurt more Americans post WWII than any other country. Either coming over the hills in Korea, or aiding and helping the Vietnamese.
IF Time can be trusted, as well as a NV I met in 1970 (and has been a ‘friend’ since) I post this. I have no time today....http://time.com/100417/china-vietnam-sino-vietnamese-war-south-china-sea/