Is there any specific proof of the part where Russia entered after Ukraine bombed??

I personally don't see it as necessary, and think an analysis of which forces/interests were pushing towards the war is more important than "who fired the first bullet" anyways. That's always seemed like a dumb way of arguing anyways, because of how often it's actually "he punched me first (after I held this knife right next to his throat for years)." But libs do all the time so it'd be good to be able to disprove not only on my terms but theirs