of course the chinese have every excuse why they need to teach Vietnam a lesson. or why the 9 dash line is there because as they claimed have discovered the sea since ancient times while we as monkeys inhabited on trees.
why should Vietnam and Russia go to war? for what reason?
sure, Vietnam owes Russia a big thank you, but you should not forget Russia had acted on her national interest too. Fighting America was in line in the interest of the Soviet Union. Similar to why the UK helped USSR. During the WW II, the British sent hundreds of convoys loading tanks, fighter planes, fuel, ammunition, raw materials and food to the Soviet Union's northern ports, to Murmask. in total
7,000 airplanes, 5,000 tanks
without the assistance of the British and later the Americans, the Red Army would have much harder to withstand the German Wehrmacht onslaughts, filling the great losses. the war could have been lost.