One way Ukraine could tangibly hurt Russia in the short-term would be to shut down the gas pipelines on their territory. Consider this map:
No doubt this would annoy the Europeans who receive Russian gas. But they’re not actively helping Ukraine just now. The Russians would be terribly angry, but they’ve already invaded.
For a country with its back against the wall, I see little downside to shutting down 66% of their invader’s cash-cow
I haven’t seen this mentioned anywhere, but I think it’s worth considering.
Historically, when Ukraine was ruled by Russia, it was considered “the breadbasket of Russia.” If Ukraine had a bad harvest, people all over Russia starved.
Of Ukraine’s top five exports, three of them are food.
So Putin invading Russia could be because he wants to secure his food supply. He’s worried he can’t feed his people, otherwise.
If so, it’s an expression of incredible insecurity on his part, not just flexing his steely authoritarian will.
Anyway. It’s just a thought.