The US did not control either Iraq nor Afghanistan when they took Baghdad or Kabul, respectively. That‘s not how a much weaker force fights nowadays against the more powerful opponent.

I believe russia has already fully integrated the idea that this will shift to a guerilla war once they have complete ownership of all the country. Nor is Ukraine (or Russia's way of maintaining control over a country once they occupy it) is really analogous to either of those countries.

I think you underestimate how easy it will be to take control of the government and country.

Ukraine knew that they would be able to take Kyiv quickly. Intelligence sources have been saying that for weeks. They (Ukraine and it's friends) have been preparing for this - openly talking about partisan style resistance.

I'm willing to bet that they need to seize pretty close to the entire country to maintain any sort of control.

I suspect Russia will just keep slicing the sausage. Then take the western provinces and re install a puppet regime as was there before (like Belarus). If that turns out to be inadequate down the road, just take another slice or two down the road.

The USSR went partially this way in Finland: sliced off half the country, though they left the other half alone, on sufferance. I don’t think Putin would be satisfied with that: he’ll want another Yanukovych or Lukashenko.

Update: I was totally wrong!