The most serious error is seeking exclusively military solutions to end hostilities.
That ship has sailed. NATO and the liberal media have convinced anyone that surrendering or negotiations mean genocide of the Ukrainian people, Russia attacking Europe and China invading Taiwan. There is a good portion of Europeans and Americans who think global thermonuclear war is preferable to Ukraine negotiating.
Russia has no choice but to grind down Ukraine slowly, like they have been doing, until Ukraine runs out of Western monetary support, weapons, and/or soldiers.
I agree. You can protect it by educating each new generation of people, among other things. Both the Soviet Union and DDR had snitches reporting people to the state, and in both the communist party failed to protect the revolution. Do you want to argue they failed because people didn’t snitch enough? That’d be interesting to see.