Yikes! I guess that "joint military exercise with Belarus" was a little more than a joint military exercise...(fuck you, Belarus)
So as we can figure out: it's a little too late for any deterrent from Russia invading Ukraine, because you know, they already have...and direct military action isn't really on the table either. I mean it is, but who really wants to go to war with a nuclear superpower? These aren't rice farmers in jungles, or guerrilla fighters in the desert. This is a well organized military with sophisticated equipment and weaponry that can go toe-to-toe with the United States and NATO. Meaning: a war with them will be a whole different warfare that no country has experienced since the last World War, and that was without the sophisticated technological advances we have today (missiles, drones, UAVs) this would be a whole different scenario with today's warfare.
We could have placed active troops alongside the Poland/Ukraine border to keep an alert eye on Russia, and to give them a sense of military presence. You know? To let Russia know, that we won't stand by while they do "military exercises"
So far this is just an invasion on the Eastern parts of Ukraine, but with a little uncertainty sprinkled here and there, Russia can claim "self-defense" giving themselves a reason to invade Ukraine in-full. (I know, it's silly. You break into someone's house and shoot the guy who's home, then claim that you were in danger)
We all know Putin isn't going to give back the areas he's already occupying, since it's a key area that chokes off Crimea. And the whole point of this invasion was to bring back former Soviet Union territories back into the Russian Federation.
So that brings the question: What can we do now that doesn't involve military conflict with Russia?
Honestly, unless you want a war with Russia, it's best to leave Ukraine and Russia to themselves, since peaceful diplomatic options are no longer on the table.
Seriously, good luck to anyone who is living in Ukraine right now, and I'm sorry that what has happened has happened.