There are now 169,000-190,000 Russian troops in and near Ukraine. In August 1968, Soviet Union moved some 350,000-400,000 Soviet troops into Czechoslovakia.

At the web page of the BBC News, I just read the following:

“Most significant military build-up in Europe since WW2 - US tells OSCE

Russia's build-up of troops along the Ukrainian border is ‘the most significant military mobilisation in Europe since the Second World War’, the US delegation to the Organisation for Security and Co-operation in Europe (OSCE) has said.

‘Rather than provide transparency and engage in risk reduction, Russia has chosen to provide disinformation and engage in denial and deception’, Michael Carpenter said, adding that there are now 169,000-190,000 Russian troops ‘in and near Ukraine’.”

https://www.bbc.com/news/live/world-europe-60428211 (18.02.2022, 14:47)

I have no doubt about the seriousness of the situation. I would just like to remind of the fact that on August 21, 1968 Soviet Union launched the Operation “Danube” moving some 350,000 to 400,000 Soviet troops accompanied by 70,000 to 80,000 combat soldiers from Poland, Bulgaria and Hungary and a liaison unit from East Germany into Czechoslovakia (figures according to Ruud van Dijk [ed.], Encyclopedia of the Cold War, Routledge 2008, p. 718). The 1968 occupation of Czechoslovakia took place 23 years after the end of the WW2 in the midst of Europe.

Sure, no significant military resistance was expected to happen nor did it happen. Still, in number of troops, a significant military operation it was.