Attacking Ukraine wasn’t as clear cut and he knew NATO wouldn’t go to war over it. Attacking a NATO country directly isn’t something our drunk Russian friends would do even though they like to rattle sabres over it. Putin has sacrificed a quarter of a million of his county’s best young men; he’s scraping the barrel now for more to turn into hamburger. In two generations those quarter of a million would have been over a million young workers in his economy. Gone. Most of his military equipment is destroyed too. He’s got nothing and he knows it. A war with NATO would be the end of Russia.