“This is their backyard and they are willing to do whatever is necessary to protect it”
They are not trying to protect. They want to annex. That’s why they are getting along with China; both are in business to gobble up neighbors.
Russia doesn’t like what’s going on in Ukraine. Bear in mind that the Ukrainian Parliament adopted legislation reinstating membership in NATO as a strategic foreign and security policy objective. This notion does not set well with Russia, a country that has experienced disastrous land invasions in the past. Look at Russian history; they have an obsession with protecting their borders.