Nation to nation war. On the way to be nuked. That's Russia doctrine - reserve right to use nuclear if Russia's territory is attacked.
I think Zelensky is losing control of Ukraine military to those ultranationalist generals. Or maybe it's a retaliation to Russia' missile attack to Ukraine command center that is said it killed 50 high ranking military officers. By any means it's embarrassing to U.S. whose military aids was claimed to not allow to attack Russia territory.