The most important lesson which should have been learned from the Vietnam War is that wars are seldom won by military means alone. We should never ever underestimate the role that propaganda plays in securing a military victory.
Both Hitler and Stalin well understood this, and they each treated language as serving just one purpose and one purpose alone - that of being God's gift to liars.
For example, in the time of the Soviet Union, the KGB actually devoted 75% of its budget - not to espionage - but to propaganda and disinformation.
From the old USSR, the Russian Federation inherited a highly effective propaganda machine; against which the likes of the New York Times, BBC and similar aren't even in the hunt!
Stalin's successors (of whatever stripe) have continued to this day making full use of what is sometimes referred to as "Hybrid Warfare" - of which the targeted use of sometimes blatant propaganda is an essential part. (And no matter how outrageous the content of such propaganda may be, there are always sufficient people around who are foolish enough to believe it). In the doctrine of hybrid warfare, propaganda rates as simply another arm to be made use of, alongside tanks, artillery, foot soldiers and aircraft.
So copious and unrelenting has the Russian propaganda effort been (ever since the time of the Soviet Union) that one commentator has described it as being, to quote, "A firehose of falsehood". This is a battle which Vladimir Putin is so far winning hands-down!
Another lesson which should have been learned from the example of Vietnam is that there are two ways of winning a war. You can either destroy the enemy's means to fight (i.e. his forces), or you can destroy his will to fight. This is another battle in which Vladimir Putin is holding all the advantages.