Well worth reading this RUSI paper.
https://rusi.org/explore-our-research/publications/special-resources/plot-destroy-ukraine
RUSI is a U.K. based think tank with strong ties to the U.K. military. It’s run by Jonathan Eyal, who I always remember watching as a kid in the late 70s on Brian Walden’s Sunday Show wax lyrical about the Soviet threat. Soviet era warriors for sure, but I think that expertise is now central to understanding Putin. He is a Soviet era Cold War warrior and I think we are moving back into a similar era if Putin goes back into Ukraine (not that he left Donbas).
See figure 2, we are likely in stage 3, on brink of stage 4, after stages 1-2 failed.