1) With an economy ranked 12th (before the sanctions) and a 4th rate military that Russia can't afford to maintain, when Putin threatens NATO, he's "punching far above his weight class!"
2) Putin is about to be introduced to the same "hard-lessons" that the Americans were taught in Iraq -
- the invasion of another country is the easy part, the subsequent occupation and dealing with insurgents is far more difficult
- the occupation and pacification of urban areas is particularly difficult, requiring far more troops that required during the initial invasion
- advantages associated with artillery, armor and technological superiority on the battlefield are largely negated in confined urban areas
- combat against insurgents in urban settings is usually an attrition war, reduced to small-scale encounters at close-quarters
- urban warfare is synonymous with high casualty rates, few decisive victories and the erosion of morale - without tangible gains to compensate for the personal sacrifices being made
3) Just as was the case in Iraq, the occupation of Ukraine is part of a familiar pattern - faced with an hostile, defiant populace requires an ever increasing commitment of financial resources, troop numbers and public support (at the cost of their sons and daughters) that eventually far outweighs whatever the benefits Putin may have envisioned, real or otherwise!